My clifford is pretty cool. Gives people 3 warnings if they are too close to the car. I can plug in my laptop in to configure the sensors, people can walk past the car, but if they stop they get a warning..
There are spare channels on the handset too so you can remote control windows, engine start, empeg etc....
It's also got a seperate fuel imob. on the tank with a wireless link back to the main unit. In the 2 1/2 years I have had it, it's only gone off twice when I didn't want it to, once when someone licked my wing mirror off and when I left my mobile in the car.

Cris.