1. A flexible, multi-modal system useful in communications among users, capable of synchronizing real world and augmented reality, wherein the system is deployed in centralized and distributed computational platforms, the system comprising: (a) a multi-modal interface comprising a sensor input interface and a sensor output interface, said multi-modal interface being designed and configured to receive and generate electronic or radio signals, said interface having a modifiable default mode for types of signals received and generated thereby; (b) a plurality of input devices designed and configured to generate signals representing speech, gestures, pointing direction, and location of a user, and transmit the same to the multi-modal interface, wherein some of the signals generated represent a message from the user intended for dissemination to other users; (c) a plurality of agents and one or more databases, (i) wherein the databases are defined by matrices which include input commands or information from one or more input devices, and meanings for some input commands or combinations thereof; (ii) wherein at least some of the agents are designed and configured to receive signals from the sensor input interface of the multi-modal interface, translate the signals into data, compare the same to a database, generate signals representing meanings as defined by the database, and transmit the signals to the multi-modal interface; (iii) wherein at least one agent resides on a computational device located on a user, and at least one other agent resides on a computation device remote from the user; and (iv) wherein at least one agent is a location-monitoring agent designed and configured to receive periodic signals representing location information of users, said signals being generated by an input device located on a user and transmitted to the multi-modal interface for further transmission to the location monitoring agent, and said agent is further designed and configured to monitor location changes of users, and in association with a database to take at least one of the following actions upon some location changes of users: (1) generate messages for transmission to the multi-modal interface, for further transmission to one or more output devices; and (2) modify the default mode of messages to another mode based upon the same or other location changes of users, such modification to be transmitted to the multi-modal interface to modify the default mode of messages generated thereby; and (d) a plurality of output devices designed and configured to receive and process signals from the sensor output interface of the multi-modal interface, some of said signals representing messages to the user to be communicated by means of an output device in visual, auditory, or tactile modes.