The Wedge Alarm, a portable door/window watchdog, would probably serve the likes of a Sayyid Jarrah or a Robert Hawkins quite well. But you? You'll probably never need this in a million years.
So here's how the thing works. You stick the wedge under the door just enough so that the door doesn't push the metal piece down too far. And when someone does open the door, it will hit the adhesive-pad secured Wedge, push the metal piece down, and sound off a buzzer at 110db.
Ok, so maybe this won't do a lot for you if some black ops badass actually kicked your door down (and he won't), but at least you'd know when your mum opened the basement door so you could stop doing whatever it is you're doing. Its available now for as low as $US5 some places. [Wedge Alarm via Toolmonger]