I have not used this part, but was recently looking at it myself. It is a simple plug and play piece that uses an external shock sensor to trigger the factory alarm.
Sensitivity can be adjusted to prevent false alarms with a simple screw on the shock sensor. It is also a 2-stage sensor, meaning it honks in short burst if it detects minor tapping on the window.
This is not like the crappy mercury switch/or spring and ball types of long ago, but a magnetic sensor. (This prevents it from being overly sensitive on inclines etc, but it is still liable to go off @ 3 in the morning when someone drives by on a Harley with his pipes uncorked!!)
It appears to be a fairly good set-up although costly ($115) compared to aftermarket (but they do not include all the plugs necessary for a clean and simple D.I.Y. installation.)
Part # 17800432 is an incline sensor which will trigger if the vehicle is slowly jacked up (for towing, or tire removal, by "Midnight Auto Supply")
PART # 17800431 SHOCK SENSOR (first picture)
PART # 17800432 INCLINE SENSOR (second picture)