CarShot

Since car alarams that merely make noise are ignored by both thieves and passers-by, what we need is a new alarm system that will effectively prevent a car being stolen.

The idea is to have a car alarm that, upon being activated by suspicious activities, will do the following: 1. Say, in a high-quality recorded voice that sounds plausibly authoritative, "Step away. Step away now!". 2. If the motion detector still senses the presence of the would-be thief, the alarm will restate the order, adding "or I will shoot you" in a voice that gets a little nervous towards the end. 3. With continued attention, the alarm will sound a single gunshot, as if a shot was fired in the air. 4. The alarm will sound three or four further "shots", this time with special effects squibs going off near where the thief is standing, that look as if the car was hit by bullets. The squib nearest the detected thief would also activate a red "blood" squib.

Obviously, this would require re-squibbing the car after every such attempt. It should still be cheaper in the long run, given the insurance savings.