I'd always imagined a car is more at risk on the street than in the driveway, but you do make a good point there...
I'm also in the market. An alarm that will go off when someone's actually trying to steal my car/something in my car, but not when the garbage truck drives by at 5am. Is the sensitivity soley down to the setup/installation of a system, or does it depend on the system itself? (obviously the number/placement of sensors will make the biggest difference, but with a typical installation)