The Computer Revolution/Security/Presence Technology
The term referring to having one device identify another device on a network is called presence technology. Presence technology can use a global positioning system (GPS) or radio frequency identification (RFID). This technology is best used for businesses because it can allow an employee to check the status of another employee without actually physically locating them. It is also used on social networks such as Facebook and IM because it shows whether the user is online or offline. Another benefit of presence technology is that it may be integrated on a mobile phone in order for it to be located if lost or stolen. Though this technology is supposed to be helpful, it could pose as a threat to privacy. 
GPS tracking is being used more and more in the Criminal Justice system to track repeat offenders and house arrest participants. The offender wears an affixed ankle bracelet and in most cases, the unit is linked to a sophisticated mapping software that will exclude zones and track specific schedules of the limitations of the offenders sentence. In more recent developments, GPS tracking can also be used in cases of domestic violence offenders and victims. The offender will wear the affixed ankle bracelet and the victim will carry a similar mobile device that will track the proximity of the offender to the victim in real time. If the offender comes within a certain distance of the victim, the offender will be called and to re-route. If the offender refuses to re-route, the local police department and victim are then notified to prepare for an encounter with the offender.
- Understanding Computers:Today and Tomorrow, Morley and Parker