Yesterday I was in a parking lot and heard a car alarm go off. Like any good citizen, I dashed over to the car to make sure it wasn’t being stolen. Ha! Did you really believe that? Car alarms are almost completely useless. A better system for car alarms is a GPS tracking device (on the lines of LoJack, but LoJack requires you to report the car stolen which could be too late by hours especially overnight) that alerts the police when the car moves without using your coded key. That is probably the most effective way to recover a stolen car.
I would definitely go for the Gps car alarm system. It just seems more reasonable.