This is sorta cool... CellTrack, a Smartphone app that pings back a server regularly to update your nearest cell tower data... effectively tracking your movement from tower to tower.

They hope to start collecting GPS data as well, and couple that with the "timing advance" data (roughly determines the round-trip time of your OTA connection) to triangulate cell tower positions.

It's pretty cool, runs on Audiovox SMT5600 phones (what I have), and is open-source should you feel like tinkering.

Right now there is not a whole lot of features, but some of the applications could be automatically turning on call-forwarding when you arrive at work or home, etc. Currently, there at least is a dynamic image generator that outputs your last 4 position/tower changes:

This really shows how bloody awful my cell coverage is here (drops signal every few minutes).

It does use GPRS to transmit updates though... Hopefully it doesnt kill my data plan limits (I rarely use the data plan from my phone anyways - too slowwww).