i have a viper alarm (currently disconnected) that has a pretty cool option. if you're driving in the ghetto, like we all do so frequently ;), you can hit a button under the dash and if you are car jacked, indicated to the alarm by the courtesy light coming on and going off (door open/close), the car will drive for 30 seconds and then the engine will die and can't be started unless you hold the button on the alarm remote and the hidden button under the dash together.