Quick and not too conclusive way: does your clown nose blink?
More conclusive way: take apart your car and check if the parts are there. It's easy to do. That square in the middle of your roof holds the ultrasonic sensor. See if something is in there. Then, pop open your hood and check if the siren is there. The tilt sensor is in the trunk but if the first two are there, it's prolly unnecessary to check that.
http://www.my330i.com/mod8.php
Use that for instructions on how to check.