THIS IS WHAT I HAVE USED AND IT WORKS!!!!!!! and is way better then LOJAK
Its called TELETRAC. It is SATELLITE monitoring system that allows you (the customer) to check the status on your vehicals location at any time of the day 24/7/365! All you do is call the toll free number, give user name and password and within 5 minutes they tell you were ur car is. The system updates every 15 seconds I think, I could be off though.
Heres the punch line.....If your car is stolen, you call the toll free number, the operator finds your vehical calls the police station in WHATEVER AND WHEREEVER city, state your car is in and the nearest patroll car will respond ASAP. Ive heard stories were stolen cars have been found in under 15 min!!!!! This is the real deal my friends.
It also has features like the ONSTAR. Hotel reservations, directions, resturants, gas stations, ect. is all justa phone call away.
For you daily drivers like myself out there, you know sometimes you park somewere and leave when 10 min later you wonder if you locked your car. No problem, call teletrac and they will lock your doors for you! Crazy huh? Works good to if you happen to lock your keys in your car

not that ive personally experienced that or something lol.
Email me
Brwnso1jah@yahoo.com or search the web for more info on the best theift deteraint system ive ever used.