Here is the Haicom HI-602DT the real time GPS tracking system which using dual module, GPS module and GSM module ( SIM card slot) as well. It using GSM dial tone transmission for transmitting position back to the tracker. You can attached it to your phone and you can put any SIM card that you want. It not make you pay monthly fees for extra messaging service.

Haicom HI-602DT feature DTMF technology through GSM voice channel to send the GPS location data to another phone. It provide route tracking on local GPS and Google maps, also able to view vehicle movements live on car navigation system’s map. It boast panic button that make the tracker send SMS with GPS location to the preset number. For detail specification of Haicom HI-602DT you can read on the source.