I just had the BMW alarm kit (Part #65 73 0 391 495) for the 330 CiC activated. While the install is very easy, the motion sensors are almost worthless! The only motions they sense is large motions that is very close to the sensor. You can remove items from the seat and door area without activate the alarm.
Furthermore your dealer may not help you if you have problems with the system without charging an arm and leg!