I've put together an Argent Data Tracker2 on a bike with the following:

Tracker2 FC/301 combination T2/301
http://www.argentdata.com/catalog/product_info.php?cPath=22&products_id=112

Batteryspace.com 1350mAH LiFePO4
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3784

Pelican P1020 Case
http://www.pelican.com/cases_detail.php?Case=1020

Byonics GPS3 module
http://www.byonics.com/tinytrak/gps.php

Here are photos:
http://wa5znu.org/2009/06/tracker2/

The photos show a 9.6V NiMH pack instead. The LiFePO4 pack is slightly
thicker and I had to remove some of the top clamshell padding to make it
fit. I stabilized the antenna with bus wire and Rescue Tape, though I'm
looking for a better soluition.

Later I plan to add a motion-activated power control mechanism, as I've
done before with a piezo element, or, given the proximity to the rear
wheel, using a magnetic reed switch:
http://wa5znu.org/2008/11/picaxe-motion-switch/

73,
Leigh/WA5ZNU