For all the people who dreamed about being able to track their vehicles by just sending SMS messages to their car, here is an article on Developing a vehicle tracker with the Telit GM862-GPS module. Great article that goes into a lot of detail on how you too can accomplish this.
Alex over at Tinkerlog has hacked together the coolest E-goodie I've seen in a while. A GSM powered GPS mobile tracker. Yeah I know, you can do it with your $1000 Nokia N95, well no you can't....you see this little guy actually sends out SMS messages (over GSM) with it's current location and since Alex has a AVR ATmega8 controller in there you can probably do some other neat hacks as well. All this for about $550, not bad. Detailed instruction/parts list to build your own are on his site.