All I had was a simple mySQL database and a PHP page to save a record. The car portion calls
http://myurl/mypage.php?lat=123.12&lon=123.12 and any other details. The web server sticks it in a table. Then a similarly simple PHP page generates links to a mapping site such as Google, GPSVisualizer etc for a "Where were you last time you uploaded" link.
The car could be set to report position every 5 minutes, or when you press a button etc.
I think another valuable mechaism is complete offline tracking where every time the car app starts it begins logging to a GPX or similar file and creates a track. Then, even if not in real time, you can find out where your car has been, how fast it went etc. Kids taking it out, mechanics at the garage going for a spin etc...
Chris.