Who the hell needs it when you have this. Just don't forget your fob for arming/disarming it in the car. If you do you're screwed.
http://tesladownunder.com/Tesladownunder's%20Car%20Theft%20Pevention%201000.jpg
http://tesladownunder.com/Tesladownunder's%20Car%20Theft%20Pevention%201000.jpg