Intro: Open GPS Tracker(Photo Instructable)
The tracker is easy to build on a perfboard. I used a basic one-pad-per-hole perfboard and 26-gauge wire, but 30-gauge would probably be better. All the electronic parts are available from Mouser Electronics. Radio Shack sells the perfboard and the 2.5mm plug for the phone. You could also buy these from Mouser.
The Mouser Electronics (http://www.mouser.com) order is listed below. This order includes an AVRISP2, which you may not need if you already have an AVR programmer. I've included two each of all the small parts, and three of the GPS module connectors. This connector is the only tricky part of the build. It is easy to ruin one, as I did. For testing, you can just insert the 26-gauge wire into the socket on the GPS module, but for permanent assembly you need the connector. The connector has one extra pair of pins, which you should cut off. You will be soldering to the long side and plugging the short side into the GPS unit.
You need to solder to four pins on the GPS header, three of which are right next to each other. Clamp the header with a small vice or a "third hand" clip. Bend the wire into a loop with pliers and attach it to the pin, then carefully solder it. I solder pin 3 and pins 7 and 11 first, putting the wires down low near the plastic separator, then solder pin 9 with the wire up high away from pins 7 and 11. Check for shorts with a meter.
pic.1--GPS module socket, module facing antenna down