Beacons versus Sensor Nodes
Beacon and sensor are terms used in short range networks used for position or presence location systems. BLE - Blue Tooth Low Power - systems are frequently used for this purpose as they interface with Bluetooth systems present in most "smart phones" and the low power consumption of BLE allows long battery life as nodes.

The following is BLE focused as this is the predominant current implementation but the majority of this material is generally applicable to other systems.

There can be overlap or full dual operation. Transmission is bidirectional and the concepts of sensor &amp; beacon  and of transmitter &amp; receiver can be blurred.  


A beacon based system tends to use distributed physically fixed-location  nodes which are detected by a portable system - typically smartphone based. The control software either resides in the phone or receives data from the phone to make decisions. The sensor (phone) tends to detect the beacons and make decisions. 
A sensor based system tends to use the fixed points as receivers which are intelligently connected to a control point, with the target phone acting as a "beacon" and its presence and activities are detected by the sensors. 


Either system can do either task given appropriate hardware and software and the boundary to how you describe a given system could change depending on how it is used and how hardware is connected or accessed.

A typical beacon system may be used in eg an art-gallery or exhibition with a user's smartphone running an "app" ( = program for olde people) that matches beason signals with specific display items or rooms etc and displays relevant information. Interaction can be arranged between user and beacon identified targets.

A typical sensor system may have a number of linked BLE "receivers" that detect smartphone Bluetooth sources and either track them or actively interact with them. 

Either type of system can be used for position location of a phone (or equivalent) within a system. Location accuracy and means of refining locations is a very black art indeed (ask me how I know) and there are numerous existing products and commercial developments being undertaken to utilise and improve on these capabilities. 



Part of the 'confusion' between sensor based and beacon based systems can be seen in the way that such systems are perceived. The OP's beacon reference Bluetooth low energy beacons says:


Bluetooth beacons are hardware transmitters - a class of Bluetooth low energy (LE) devices that broadcast their identifier to nearby portable electronic devices. The technology enables smartphones, tablets and other devices to perform actions when in close proximity to a beacon.[1][2]
Bluetooth beacons differs from some other location-based technologies as the broadcasting device (beacon) is only a 1-way transmitter to the receiving smartphone or receiving device, and necessitates a specific app installed on the device to interact with the beacons. This ensures that only the installed app (not the Bluetooth beacon transmitter) can track users, potentially against their will, as they passively walk around the transmitters.
Bluetooth beacon transmitters come in a variety of form factors, including small coin cell devices, USB sticks, and generic Bluetooth 4.0 capable USB dongles.[9]


While the above is generally true it is not so by definition. The technology is usually BLE based and so can do whatever BLE can do - so is by no means confined to unidirectional communications and even in "beacon" mode a module returns a signal strength indication to the "sensor" which is utilised in various ways by essentially all systems. 

Similarly the Op's Sensor node reference is correct enough in what it says but "fails to blur" the boundary between  beacons and sensors in any way. The term "beacon" does not appear at all in the text.

Wireless "nodes" are far from new and it follows that most conceivable 'perms and coms' will have been investigated.
This wikipedia page of around 150 known Wireless sensor nodes will be incomplete but shows how much effort has gone into the general area. As an indication of the detail provided this shows the table's column headings.

    TECHNOLOGY  MCU OPERATING SYSTEM    CONNECTIVITY    INTERFACES  SENSORS DIMENSIONS (mm) ENERGY  APPS    MEMORY  SERVICES
NAME    MANUFACTURER    PRICE   RELEASE ARCH    DEVICE  CLOCK   RTC TinyOS  ContikiOS   Others  Bluetooth   Wi-Fi   802.15.4    ZigBee  XBee    6LoWPAN WirelessHART    I2C/TWI SPI UART    GPIO    USART   USB ADC DAC Timers  JTAG    Others  Temperature Humidity    Luminosity  Pressure    Gyroscope   Accelerometer   CO2 Motion  Acoustic    Others  Length  Width   Height  Voltage Sleep   Nominal Radio RX    Radio TX    PoUSB   OTAP    SDK RAM Program Memory  Data Memory Flash   HTTP    UDP TCP IPv4    IPv6    RPL CoAP    API Other


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BLE Beacons  just a basic Garglabet search BUT many good quality matches - scrolling down the list for several 'pages', every hit seemed relevant and probably useful 

BLE sensors - same for sensors.

BLE sensors - images an extremely informative list - each image is useful in its own right and links to a related page. 

BLE position location - anothe Garglabet search - but still useful.
Tutorials, basic introductions, commercial products, ... .
and images

Examples

Museum position location system

Conference tracking system beacon emphasis.

Slideshow discussing many approaches

Shoplitics - Chinese language - translate with Gargoyle or whatever - messay result but worth a look as tendency to be sensor based using users phones as beacons but can also add mobile beacons to shopping baskets etc. An example of a potentially duel mode system.

EEtimes on position location 2015 but useful. Discusses integration/fusion for location improvement.

Wikipedia - BLE

TI - BLE - TI make a range of BLE ICs targeted at beacon/sensor use and with FCC approvals. The lowest power versions allow multi-year operation on small coin cells. One variant includes their "SimpleLink" multi-standard 2.4 GHz wireless MCU with code compatibility across Bluetooth low energy, 6LoWPAN, ZigBee® and ZigBee RF4CE™ by downloading the corresponding protocol stack

Bluetooth.com

Android developers - BLE

ARMmbed

Safari - getting started

Cypress semiconductors - BLE

Adafruit - BLE node/sensor

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Shoppertrack


A BLE beacon is a small device – usually powered by battery or USB – that emits a Bluetooth Low Energy signal. A modern smartphone in the vicinity can pick up the signal being emitted by the beacon and gain some insight into its own positioning based on knowledge of the beacon’s placement.
It is important not to confuse BLE with “classic” Bluetooth; despite falling under the same name, they are entirely different technologies. Bluetooth consumes more power and transmits farther and with more data. It is suited for streaming media such as playing music on Bluetooth speakers or taking a call through a Bluetooth headset. BLE transmits less data over shorter distances using much less power than Bluetooth. BLE is designed for periodic transfers of very small amounts of data, such as beacons providing proximity in a store or a medical device providing glucose measurements to a doctor’s tablet or patient monitor.
To further confuse things, Apple has their own implementation of BLE that they call iBeacon. Apple’s iBeacon defines what is communicated over BLE and at what interval. How the data is transmitted is still defined by the BLE specification.


Range aspects

Slideshow - some use

Fully Distributed Monitoring Architecture Supporting Multiple Trackees and Trackers in Indoor Mobile Asset Management Application and PDF

WiFi - Indoor Human Localization with Orientation using
WiFi Fingerprinting

CISCO - WiFi location fingerprinting

Fusion [tm] Fusion of WiFi, Smartphone Sensors and Landmarks Using the Kalman Filter for Indoor Localization and PDF

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Kickstarter -  IOT hat - BLE beacon Raspberry Pi / Arduino / ...  interface :-) and here



Privacy issues - this and related technologies.



Location accuracy:

Weighted Least Squares Techniques for Improved Received Signal Strength Based Localization open access full test

BLE accuracy using Estimotes

An Analysis of the Accuracy of Bluetooth Low
Energy for Indoor Positioning Applications