Really?

You can build a TNC for about $30[1], and get a serial GPS module for $40[2]. If you are using a PC you can use a sound card modem[3] for virtually no cost, and you may already have a GPS with serial output. If it's a Garmin you'll need a cheap cable[4]. There is also cheap/free software for Windows, Mac and Linux. If you don't want to use a PC you can use the TNC in [1] as a tracker, or build this one[5] for a few dollars.

73!

[1] http://www.enide.net/webcms/index.php?page=wb8wga-tnc
[2] http://www.amazon.com/BR-BR-355-Serial-GPS-Reciever/dp/B000WA1M8M
[3a] http://www.baycom.org/~tom/ham/soundmodem/
[3b] http://www.soundcardpacket.org/index.html
[4] http://www.pfranc.com/
[5] http://www.ringolake.com/pic_proj/gps_trak/freetrak202.html