I've got a teen driver I like to keep tabs on. We bought the tracking device from InTouch. Before you yell at me for violating her privacy, she knows we've got it, and it's proven helpful when she's gotten lost or needed a jump start--but couldn't tell me clearly where the car was. http://www.intouchmvc.com/gps-teen-tracking.html
I think it was $249 plus $10 per month, or 6 months for $100. It plugs into the OBD for newer cars...and they have a hard-wired version available at the same price for older cars.
Once you activate the device you're given a personal web page. At any time, you can see a realtime view of where the vehicle is and if it's in motion, it's speed. You can set it up for notifications, where you'll receive text messages or emails for events you designate (car in motion, car stopped, entering or leaving a geographic boundary, exceeding a pre-set speed, etc.). It works extremely well, and would be just the ticket for locating a stolen car.