Tracker attached at vehicle will accept coordinates from GPS satellites, Coordinates that accepted by the tracker will be delivered to monitoring application through media of GPRS or satellite (depended from type of tracker) and monitoring application will translate vehicle position along with all status of vehicles [e.g.: door open/close; engine on/close] at a digital map in computer monitoring screen.
In Indonesia This GPS tracking system was begin in 2005. Many company come in to this field, these are several of the list:
Vi-Track, http://news.vi-track.com
Solo System, http://solosystem.net
Indo-GPS, http://indogps.com
InovaTrack, http://www.inovatrack.com
Ctrack, http://ctrackindonesia.com
Tramigo, http://www.tramigo.net
A few of Tracker pictures :