I like the idea of sending you car a message to disable the ECU if it's stolen. Check for a thread called "GPSsecure" for a program by xBrady that logs your position, altitude, velocity, and uploads the file to a server. You can recall the info from the server through a desktop program he has written.
Here's the location of my car at 8:25am this morning. I've pulled in front of the school and am droppping my kids off.