I read an article just this morning about the rental companies using GPS devices to record where/when/how fast you drive their cars. A friend works for PacBell and they track him with a GPS device. When he stops for lunch the supervisers get an alert if the truck sits for more that thirty minutes. Most of the 'track your teen' devices are GPS. Company cars are getting similar devices. There are good uses for this technology. On-Star will call you (your vehicle actually) if the airbag deploys. If you confirm an accident or don't reply they send help to your location.
Here is a link to the article.
http://www.zdnet.com/anchordesk/stor...913976,00.html