Ok, here's an idea.

Install some 802.11b in the car (probably Linksys WAP11 or WET11) and have it scan for open WLANs. When one is found, connect back to your personal web server and upload your current location (from gpsd) and the server logs the time.

Why?
- Historical map of where you've driven and when
- Wardriving record of where the open WLANs are
- If your car gets stolen, you can tell the police exactly where it is
- Maybe contact a central web server to locate other empeg users

Possible?
- Can something like a WET11 automatically scan for open WLANs?