FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to location tracking, and, more specifically, to techniques for mobile geofencing. 
     BACKGROUND OF THE DISCLOSURE 
     Geofencing allows an administrator to define an area that a user is not allowed to leave. For example, a parent may say that their child should only be at home, school, or somewhere in between. An employer may say that their truck drivers should only be on their delivery routes. If the geofencing policy is violated, then the administrator is alerted. 
     However, real world scenarios are rarely this static. For example, a child may leave home in the company of his or her parent, on the public school bus, or on a specific city bus that takes them to a relative&#39;s house. This makes for a poor user experience, as a parent gets notifications and perhaps disables geofencing policy whenever they are out and about with their child. It also lowers security, as the child should continue to be tracked and alerted on if they wonder (or are taken) outside of the parent&#39;s vicinity. 
     In view of the foregoing, it may be understood that there may be significant problems and shortcomings associated with current geofencing technologies. 
     SUMMARY OF THE DISCLOSURE 
     Techniques for mobile geofencing are disclosed. In one embodiment, the techniques may be realized as a method comprising the steps of receiving geofence parameters comprising at least one target, wherein the at least one target includes a mobile target; receiving updated position data associated with the mobile target and updating the position of the mobile target in response to the updated position data; monitoring a position of a client device; and determining that the monitored position of the client device transgresses the geofence parameters, wherein the determination includes determining that a distance between the updated position of the mobile target and the monitored position of the client device is greater than a first threshold distance. 
     In accordance with other aspects of this embodiment, the method may further comprise generating a notification in response to determining that the monitored position transgresses the geofence parameters. 
     In accordance with other aspects of this embodiment, the at least one target may be a plurality of targets, the plurality of targets further including a stationary geographic position. Determining that the monitored position transgresses the geofence parameters may further include determining that a distance between the stationary geographic position and the monitored position is greater than a second threshold distance. 
     In accordance with further aspects of this embodiment, the first threshold distance may be the same as the second threshold distance. 
     In accordance with further aspects of this embodiment, in response to determining that the distance between the stationary geographic position and the monitored position is greater than a second threshold distance, the method may further include requesting updated position data associated with the mobile target. The updated position data may be received after requesting updated position data. 
     In accordance with other aspects of this embodiment, the geofence parameters may include one or more stationary geofence parameters. Determining the distance between the updated position of the mobile target and the monitored position of the client device may occur in response to determining that the monitored position transgresses the one or more stationary geofence parameters. 
     In accordance with other aspects of this embodiment, the first threshold distance may be a user-predetermined setting. 
     In accordance with other aspects of this embodiment, the geofence parameters may further include a stationary geographic border. Determining that the monitored position transgresses the geofence parameters may further includes determining that the monitored position transgresses the stationary geographic border. 
     In accordance with further aspects of this embodiment, the method may further include, in response to determining that the monitored position transgresses the stationary geographic border, requesting updated position data associated with the mobile target. The updated position data may be received after requesting updated position data. 
     In accordance with another embodiment, the techniques may be realized as an article of manufacture including at least one processor readable storage medium and instructions stored on the at least one medium. The instructions may be configured to be readable from the at least one medium by at least one processor and thereby cause the at least one processor to operate so as to carry out any and all of the steps in the above-described method. 
     In accordance with another embodiment, the techniques may be realized as a system comprising one or more processors communicatively coupled to a network; wherein the one or more processors are configured to carry out any and all of the steps described with respect to any of the above embodiments. 
     The present disclosure will now be described in more detail with reference to particular embodiments thereof as shown in the accompanying drawings. While the present disclosure is described below with reference to particular embodiments, it should be understood that the present disclosure is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein, and with respect to which the present disclosure may be of significant utility. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to facilitate a fuller understanding of the present disclosure, reference is now made to the accompanying drawings, in which like elements are referenced with like numerals. These drawings should not be construed as limiting the present disclosure, but are intended to be illustrative only. 
         FIG. 1  shows a block diagram depicting a network architecture in accordance with an embodiment of the present disclosure. 
         FIG. 2  shows a block diagram depicting a computer system in accordance with an embodiment of the present disclosure. 
         FIG. 3  shows a block diagram of a mobile client device, mobile target, and monitoring server in accordance with an embodiment of the present disclosure. 
         FIG. 4  shows a method for geofencing in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present disclosure relates to improving usability and security of existing geofencing solutions by allowing an administrator to define dynamic geofences around people and other moving objects. 
     When defining the geofence, the administrator can identify mobile points of reference such as people and vehicles that are equipped with geographic location tracking such as (but not limited to) GPS, mobile phone tracking, radar, etc. The administrator can then define radiuses around these reference points within which the monitored user (e.g. the child) can be considered within the geofence. This allows, for example, a parent to send his or her child to a city bus stop and only be notified if the child does not get off on the expected stop (as many cities now equip public buses with trackable GPS). It also allows the parent to accompany the child outside of the static geofence without alerts or disabling tracking, and still get alerts if the child wanders off or is taken. 
     The present disclosure includes optionally using new or existing social networks to improve usability of configuring dynamic geofences. Users can identify a Facebook friend as a safe mobile point of reference. The present disclosure also includes optionally using a third party source of GPS such as Glympse. Users can also identify online event scheduling resources as a way to automatically adjust the geofence to account for one-time or recurring events—for example, the parent could pre-authorize events listed in their child&#39;s school&#39;s Facebook profile or Google calendar in order to automatically adjust the geofence to include school buses and museums as appropriate. 
       FIG. 1  shows a block diagram depicting a network architecture  100  in accordance with an embodiment of the present disclosure.  FIG. 1  is a simplified view of network architecture  100 , which may include additional elements that are not depicted. Network architecture  100  may contain client systems  110 ,  120  and  130 , as well as servers  140 A- 140 N (one or more of each of which may be implemented using computer system  200  shown in  FIG. 2 ). Client systems  110 ,  120  and  130  may be communicatively coupled to a network  150 . Server  140 A may be communicatively coupled to storage devices  160 A( 1 )-(N), and server  140 B may be communicatively coupled to storage devices  160 B( 1 )-(N). Servers  140 A and  140 B may be communicatively coupled to a SAN (Storage Area Network) fabric  170 . SAN fabric  170  may support access to storage devices  180 ( 1 )-(N) by servers  140 A and  140 B, and by client systems  110 ,  120  and  130  via network  150 . 
     With reference to computer system  200  of  FIG. 2 , modem  247 , network interface  248 , or some other method may be used to provide connectivity from one or more of client systems  110 ,  120  and  130  to network  150 . Client systems  110 ,  120  and  130  may access information on server  140 A or  140 B using, for example, a web browser or other client software (not shown). Such a client may allow client systems  110 ,  120  and  130  to access data hosted by server  140 A or  140 B or one of storage devices  160 A( 1 )-(N),  160 B( 1 )-(N), and/or  180 ( 1 )-(N). 
     Networks  150  and  190  may be local area networks (LANs), wide area networks (WANs), the Internet, cellular networks, satellite networks, or other networks that permit communication between clients  110 ,  120 ,  130 , servers  140 , and other devices communicatively coupled to networks  150  and  190 . Networks  150  and  190  may further include one, or any number, of the exemplary types of networks mentioned above operating as a stand-alone network or in cooperation with each other. Networks  150  and  190  may utilize one or more protocols of one or more clients or servers to which they are communicatively coupled. Networks  150  and  190  may translate to or from other protocols to one or more protocols of network devices. Although networks  150  and  190  are each depicted as one network, it should be appreciated that according to one or more embodiments, networks  150  and  190  may each comprise a plurality of interconnected networks. 
     Storage devices  160 A( 1 )-(N),  160 B( 1 )-(N), and/or  180 ( 1 )-(N) may be network accessible storage and may be local, remote, or a combination thereof to server  140 A or  140 B. Storage devices  160 A( 1 )-(N),  160 B( 1 )-(N), and/or  180 ( 1 )-(N) may utilize a redundant array of inexpensive disks (“RAID”), magnetic tape, disk, a storage area network (“SAN”), an internet small computer systems interface (“iSCSI”) SAN, a Fibre Channel SAN, a common Internet File System (“CIFS”), network attached storage (“NAS”), a network file system (“NFS”), optical based storage, or other computer accessible storage. Storage devices  160 A( 1 )-(N),  160 B( 1 )-(N), and/or  180 ( 1 )-(N) may be used for backup or archival purposes. Further, storage devices  160 A( 1 )-(N),  160 B( 1 )-(N), and/or  180 ( 1 )-(N) may be implemented as part of a multi-tier storage environment. 
     According to some embodiments, clients  110 ,  120 , and  130  may be smartphones, PDAs, desktop computers, a laptop computers, servers, other computers, or other devices coupled via a wireless or wired connection to network  150 . Clients  110 ,  120 , and  130  may receive data from user input, a database, a file, a web service, and/or an application programming interface. In some implementations, clients  110 ,  120 , and  130  may specifically be network-capable mobile devices such as smartphones or tablets. 
     Servers  140 A and  140 B may be application servers, archival platforms, backup servers, network storage devices, media servers, email servers, document management platforms, enterprise search servers, or other devices communicatively coupled to network  150 . Servers  140 A and  140 B may utilize one of storage devices  160 A( 1 )-(N),  160 B( 1 )-(N), and/or  180 ( 1 )-(N) for the storage of application data, backup data, or other data. Servers  140 A and  140 B may be hosts, such as an application server, which may process data traveling between clients  110 ,  120 , and  130  and a backup platform, a backup process, and/or storage. According to some embodiments, servers  140 A and  140 B may be platforms used for backing up and/or archiving data. One or more portions of data may be backed up or archived based on a backup policy and/or an archive applied, attributes associated with the data source, space available for backup, space available at the data source, or other factors. 
     According to some embodiments, clients  110 ,  120 , and  130  may contain one or more portions of software for implementation of geofencing processes such as, for example, geofencing application  154 , while server  140 A may include one or more portions such as, for example, geofencing module  156 . Further, one or more portions of the geofencing module  156  may reside at a network centric location. For example, server  140 A may be a server, a firewall, a gateway, or other network element that may perform one or more actions to support management of system and network security elements. According to some embodiments, network  190  may be an external network (e.g., the Internet) and server  140 A may be a gateway or firewall between one or more internal components and clients and the external network. According to some embodiments, analysis and approval of resource references including geofencing module  156  may be implemented as part of a cloud computing environment. 
       FIG. 2  shows a block diagram of a computer system  200  in accordance with an embodiment of the present disclosure. Computer system  200  is suitable for implementing techniques in accordance with an embodiment of the present disclosure. Computer system  200  may include a bus  212  which may interconnect major subsystems of computer system  200 , such as a central processor  214 , a system memory  217  (e.g. RAM (Random Access Memory), ROM (Read Only Memory), flash RAM, or the like), an Input/Output (I/O) controller  218 , an external audio device, such as a speaker system  220  via an audio output interface  222 , an external device, such as a display screen  224  via display adapter  226 , serial ports  228  and  230 , a keyboard  232  (interfaced via a keyboard controller  233 ), a storage interface  234 , a floppy disk drive  237  operative to receive a floppy disk  238 , a host bus adapter (HBA) interface card  235 A operative to connect with a Fibre Channel network  290 , a host bus adapter (HBA) interface card  235 B operative to connect to a SCSI bus  239 , and an optical disk drive  240  operative to receive an optical disk  242 . Also included may be a mouse  246  (or other point-and-click device, coupled to bus  212  via serial port  228 ), a modem  247  (coupled to bus  212  via serial port  230 ), network interface  248  (coupled directly to bus  212 ), power manager  250 , and battery  252 . 
     Bus  212  allows data communication between central processor  214  and system memory  217 , which may include read-only memory (ROM) or flash memory (neither shown), and random access memory (RAM) (not shown), as previously noted. The RAM may be the main memory into which the operating system and application programs may be loaded. The ROM or flash memory can contain, among other code, the Basic Input-Output system (BIOS) which controls basic hardware operation such as the interaction with peripheral components. Applications resident with computer system  200  may be stored on and accessed via a computer readable medium, such as a hard disk drive (e.g., fixed disk  244 ), an optical drive (e.g., optical drive  240 ), a floppy disk unit (not shown), a removable disk unit (e.g., Universal Serial Bus drive), or other storage medium. According to some embodiments, geofencing application  154  may be resident in system memory  217 . 
     Storage interface  234 , as with the other storage interfaces of computer system  200 , can connect to a standard computer readable medium for storage and/or retrieval of information, such as a fixed disk drive  244 . Fixed disk drive  244  may be a part of computer system  200  or may be separate and accessed through other interface systems. Modem  247  may provide a direct connection to a remote server via a telephone link or to the Internet via an internet service provider (ISP). Network interface  248  may provide a direct connection to a remote server via a direct network link to the Internet via a POP (point of presence). Network interface  248  may provide such connection using wireless techniques, including digital cellular telephone connection, Cellular Digital Packet Data (CDPD) connection, digital satellite data connection or the like. GPS unit  238  may receive position information, such as the standardized signals sent by the global positioning system, and may be configured to provide position information based on the received signals. 
     Many other devices or subsystems (not shown) may be connected in a similar manner (e.g., document scanners, digital cameras and so on). Conversely, all of the devices shown in  FIG. 2  need not be present to implement an embodiment of the present disclosure. The devices and subsystems can be interconnected in different ways from that shown in  FIG. 2 . Code to implement an embodiment of the present disclosure may be stored in computer-readable storage media such as one or more of system memory  217 , fixed disk  244 , optical disk  242 , or floppy disk (not shown). Code to implement an embodiment of the present disclosure may also be received via one or more interfaces and stored in memory. The operating system provided on computer system  200  may be MS-DOS®, MS-WINDOWS®, OS/2®, OS X®, UNIX®, Linux®, or another known operating system. 
     Power manager  250  may monitor a power level of battery  252 . Power manager  250  may provide one or more APIs (Application Programming Interfaces) to allow determination of a power level, of a time window remaining prior to shutdown of computer system  200 , a power consumption rate, an indicator of whether computer system is on mains (e.g., AC Power) or battery power, and other power related information. According to some embodiments, APIs of power manager  250  may be accessible remotely (e.g., accessible to a remote backup management module via a network connection). According to some embodiments, battery  252  may be an Uninterruptable Power Supply (UPS) located either local to or remote from computer system  200 . In such embodiments, power manager  250  may provide information about a power level of an UPS. 
     In one embodiment, a client system  110  may be a mobile device  300  as illustrated in  FIG. 3 . The mobile client device  300  may include a GPS module  302  that monitors received global positioning signals and uses those signals to determine a position for the client device  300 . In some implementations, the GPS module  302  may further control a GPS receiver unit and other units associated with receiving and signaling position. Once the GPS receiver unit determines position information, the information may then be relayed to other applications for further use in navigation and tracking, such as a geofencing application  154 . 
     The geofencing application  154  may communicate with the geofencing module  156  of a server  104 A. The application  154  may report position information to the module  156  at regular intervals, or in response to certain events determined at the client device  300 , or in response to a request for position information from the module  156 . In some implementations, the geofencing application  154  may not be a standalone application, but instead may be a feature of another application, of an operating system, of a module such as the GPS module, or the like. 
     The geofencing module  156  may include geofencing parameters  322 , which specify where the mobile client device  300  is permitted to be. The geofencing parameters may include, for example, one or more stationary positions and an allowed distance from each of those stationary positions; the allowed distances may be the same or may be different. The geofencing parameters may include, for example, one or more borders and a side of each border that the client device is permitted to be on. These stationary parameters may further include one or more navigation routes, which may represent an allowed region between two stationary positions such that the client device is permitted to be within a set distance of either stationary position or along the route between the stationary positions. Other settings, options, and configurations for stationary geofencing are known in the art. 
     In addition to the stationary geofencing parameters, the geofencing parameters  322  further include one or more mobile targets, represented by the mobile target  310 . A distance may be associated with each mobile target  310 , such that the client device  300  is in a permitted location as long as it is within the associated distance of a mobile target  310 . Each mobile target distance may be the same or different and may be the same as or different than distances associated with the stationary targets. Mobile target  310  may be any target with variable position information, such as a client device, private vehicle, or public transit. The mobile target  310  may have a GPS module  312  or may have position information that is tracked in another fashion. 
     The geofencing module  156  may include a client monitor  324 , which monitors the position and status of the client device  300  in accordance with the geofencing parameters  324 . The client monitor  324  may communicate with a geofencing application  154  on the client device  300 , may otherwise communicate with the client device  300 , or may retrieve information about the client device  300  indirectly, such as from another system in network communication with the client device  300 . In some implementations, the client monitor  324  may receive information from a service network providing telephone or data service to the client device  300 . The device information monitored may include position information but also device status, such as the level of battery charge, whether the device is in a special operating mode such as “hands-free” or “airplane,” and whether the device is connected to a wireless network. 
     The geofencing module  156  may include a mobile target monitor  326 , which may include any of the features of the client monitor  324  in order to determine position and other status information for the mobile target  310 . The mobile target monitor  326  may receive information from the mobile target  310  indicating the target&#39;s current position, or may receive information from a third party. In some implementations, the mobile target monitor  326  may receive information from a public transit system regarding the position of a mobile target  310  that is a transit vehicle. 
     In some implementations, the mobile target monitor  326  may not be as active as the client monitor  324 . For instance, the client monitor  324  may monitor a client device  300  at regular intervals, while in some implementations the position of the mobile target  310  may only be queried and monitored when the device  300  is otherwise outside of the stationary geofencing parameters  300 . In some implementations, position data may be sent regularly to the client monitor  324  but may only be sent to the mobile target monitor  326  when explicitly requested. 
     The geofencing module  156  may further include a transgression calculator  328  which compares the position of the client device  300  with the geofencing parameters  322  to determine if the client device  300  has transgressed the geofence. In some implementations, the transgression calculator  328  may first evaluate the position of the client device  300  against the stationary geofencing parameters, and only query the mobile target monitor  326  for the geofencing parameters associated with the mobile target or targets if the mobile device  300  is outside the stationary parameters. 
     The geofencing module  156  may further include an alert generator  330 , which may generate a notification event, an alarm, or other alert in response to a transgression of the client device  300  as determined by the transgression calculator  328 . In some implementations, a communications module  332  may be used to provide an alert, which in some implementations may include a message such as an email or SMS message. A push or other application notification may also be sent as an alert. 
       FIG. 4  illustrates a method  400  for geofencing. The system monitors the position of a mobile client ( 402 ). The system may receive data from the mobile client reflecting a position, such as GPS data from an on-board GPS unit; the system may also receive data from other systems, such as communications systems providing network connectivity to the mobile client. In some implementations, the system may request data from the mobile client; alternatively, the mobile client may send position data to the system at a particular interval or in response to a particular event. 
     The system determines whether the position of the client satisfies the constraints of the stationary parameters or transgresses them ( 404 ). It will be noted that the position of the mobile client is not always precisely determinable; in some implementations, an imprecise range may be determined for the client position and the system may have to determine whether to consider the client to be transgressing the parameters based on ambiguity in the client location. The system may, in some implementations, determine a probability distribution for the position of the mobile device based on the reported error and a record of the client&#39;s previous positions, and consider the client to have transgressed only if a probability of a transgressing location exceeds a threshold value. The constraints of the stationary parameters may also represent geofencing parameters known in the art; that is, one of ordinary skill may recognize stationary geofencing and how to determine transgression. Other techniques to deal with ambiguous location in stationary geofencing are also known in the art. If the mobile client is considered to be within the stationary geofencing parameters, the system continues to monitor the client position. 
     According to the method  400  of  FIG. 4 , which is only one possible method to implement a process in accordance with an embodiment of the present disclosure, if the client is found to have transgressed the stationary parameters, the positions of the mobile targets are acquired ( 406 ). Ambiguous or imprecise locations are also possible for each of the mobile targets; in some implementations, a history of mobile target positions may be maintained and range of allowed positions may be implemented based on imprecise locations. Particular mobile targets whose positions are not reported at all in response to a system query may not be included in the analysis. 
     The positions of the mobile targets are then compared to the position of the mobile client to determine if the mobile parameters are also transgressed ( 408 ). Where both the mobile client and a particular mobile target include an uncertainty and a potential area of location, an overlap area may be calculated and compared against a threshold overlap to determine whether the mobile client should be considered within proximity of the mobile target. If the mobile client is within the specified distance of any of the mobile targets, then the mobile system returns to monitoring the client position. 
     If the client device is found to transgress the mobile parameters as well, then the system may generate an alert ( 410 ). The alert may be any message or communication designed to identify that a transgression event has occurred. In some implementations, the alert may be given to a third party such a monitoring service or to the authorities. The alert may include a notification to the client device, such as an application notification or SMS message. Alternatively, the client device itself may not be included in the alert. 
     In some implementations, the generation of an alert may temporarily stop the geofencing process, although some monitoring of the mobile client device may continue. In some implementations, further monitoring (including additional alerts) may be possible after a set interval. 
     At this point it should be noted that geofencing in accordance with the present disclosure as described above may involve the processing of input data and the generation of output data to some extent. This input data processing and output data generation may be implemented in hardware or software. For example, specific electronic components may be employed in a mobile device or similar or related circuitry for implementing the functions associated with geofencing in accordance with the present disclosure as described above. Alternatively, one or more processors operating in accordance with instructions may implement the functions associated with geofencing in accordance with the present disclosure as described above. If such is the case, it is within the scope of the present disclosure that such instructions may be stored on one or more non-transitory processor readable storage media (e.g., a magnetic disk or other storage medium), or transmitted to one or more processors via one or more signals embodied in one or more carrier waves. 
     The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been presented herein in the context of at least one particular implementation in at least one particular environment for at least one particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.
Techniques for mobile geofencing may be realized as a method including: receiving geofence parameters comprising at least one target, wherein the at least one target includes a mobile target; receiving updated position data associated with the mobile target and updating the position of the mobile target in response to the updated position data; monitoring a position of a client device; and determining that the monitored position of the client device transgresses the geofence parameters, wherein the determination includes determining that a distance between the updated position of the mobile target and the monitored position of the client device is greater than a first threshold distance.