Before this, AFAIK, we only had to worry about getting a GPS transmitting device planted on our vehicles, which would be bulky enough to spot fairly easily by anyone checking out the cars underside, etc. Here's one that doesn't transmit, just records where you go, and that info can be retrieved later ala bluetooth from 30 feet away.
http://www.blackboxgps.com -- Harmon Seaver CyberShamanix http://www.cybershamanix.com
