Where there are cars, unfortunately, there are car thieves. And where there are car thieves, there is a need for car alarms. Car alarms can alert a car owner if someone is tampering with or entering their car without their permission. Car alarms serve a useful purpose in that they do deter some crime by frightening away some would be car thief and if they are within earshot, the car owner, at the first sound of his car alarm can come and investigate and possibly save their vehicle from theft or vandalism. At least that is the whole idea behind car alarms. The reality of it is something else altogether.