For those who use tow-truck to steal the car, tilt sensor is the item that can help to delay their process. The tilt sensor kicks in when you park your car, means once you park your car, the direction of the sensor sets at a particular angle.
Let's say your car is being tow-ed and the alarm is still in arm mode, once the car turns even just a few degrees, the tilt sensor will trigger the alarm. True, the car can be still stolen away if the thieves ignore it and continue to tow it (if they really wants to steal it), but what the alarm can do is to create "attention" and "awareness" at the surrounding area, then it is up to the public to report to the nearby police. If lucky, the thieves will abandon the car since the siren is beeping.
And not to forget, do install a back-up battery at a hidden area because thieves can disarm the alarm by just disconnecting the battery terminal.