gps.......?

i have a extra gps tracking devise. it says legent and garmin on it. it locates way points and stuff like that. i was wondering if you could put it on someones car and track were they're going without you there and without them knowing. can anyone give

Nope. The Garmin eTrex Legend is a handheld GPS device that will pinpoint your location when you're out trekking or just walking about. It doesn't track your whereabouts.
For that you need a GPS tracking device like the Trackstick or i-gotu GPS

GPS 800G watch phone gets the job done (and little else) -- Engadget

The GPS 800G -- delivered by none other than Shanghai Zhiyuan Vacuum Electric Company, of course -- manages to handle time telling, texting, GPS routing and even emergency calling. Given that we're probably years, if not centuries, away from that happening, it's up to niche import shops like Alibaba to bring us goods like these. Your captor would be able to hear any attempt at a voice call so your ability to write text messages would be very important to alert the authorities. Looks as if you'll need to ping the supplier in order to get a lock on pricing, but we can't say with a straight face that it'll be worth your while. Watch phones clearly haven't hit the mainstream yet, though a resurgence of Dick Tracy may very well turn that around. Oh, and normal calling as well....