Shahin, I purchased it from Car Audio Systems in Mt View, CA.
ImolaEd, here is how the carjacking works.
Whenever you are in a bad area, you activate the carjacking device. This requires that you enter a code each time you open and close your doors. If you forget, there is a warning chirp that prompts you. Failure to do so within the required 30 seconds, the doors will lock, the engine will shut off and the alarm will activate.
So if I ever get carjacked, I just hand them the car and within 1 block the car will stop running.
Feel free to let me know if you have anymore questions.