Purchase a WhereSafe GPS device, and pick your service plan when you Activate the device. Plans are $12.95/month, or $139.95/year (For a Limited Time: Get a $40.00 hardware rebate when choosing a Yearly Plan and pay only $99.95 for the first year!).
Magnetic GPS Tracker
Sport Tracker (Wired & Hidden GPS Tracker)
Plug-In GPS Tracker (OBDII)