I just had this idea for a motion sensing and motion tracking camera placed hanging from the ceiling inside a window, and rigged up to pull up the horizontal blinds it is aimed at when motion is detected, both for a clearer picture and to startle the ever-living shit out of any would-be intruder. If they stick around long enough to notice the camera, it should be enough to convince them it's a bad idea to stay. It should also produce a good source of hilarious photos!