Whats the best thief protection device available?

[RPM427]

I have a friend that is really big into stereos and stereo competitions. He has had about $10,000 worth of stereo equipment stolen out of his car (2 break ins) off campus while at school. He has always had an expensive alarm on it (I think its from audiovox, that pages him and will tell him what door is open and if the windows have been broken, etc) . That didn't seem to help him cuase the assholes would have loaded the stereo into thier car and driven away by the time we got to his car. He got sick of this and mounted a few piezo sirens in the car. I have heard these go off standing accross the parking lot and had to cover my ears and turn away. If the alarm senses a window break or a door/trunck/hood opening while the alarm is armed, it will set these things off. The manufacterer claims that the sound (if you are in the car trying to steal something) will make you VERY disoriented and make you want to throw up. It is impossible for someone to be with in 10 feet of the car for more then a few seconds, let alone in it triing to steal the stereo. he has had his car broken into but nothing was stolen.