Our pals at Makezine noticed this write-up in Popular Science on a low cost way to do your own cell phone tracking using the Mologogo service:

Cue the Mission Impossible theme. I’m working a top-secret operation, and my support team is monitoring my every movement. OK, so I’m just going to the hardware store, but my girlfriend, Jen, is tracking me. Using a $100 kit from Mologogo (with a $6-a-month data plan), I’ve turned a prepaid cellphone into a GPS tracking device. Every few minutes, the phone transmits my location within 100 meters to mologogo.com, which posts it to a Google map that Jen can access from any computer. She can view my most recent spot or my past 100 recorded locations as little pushpins stamped with date and time.