Last night whilst looking at our ceiling fan, I had a flash of inspiration and realised that it could be incorporated into a booby-trap of sorts. I immediately began work on creating such a contraption:
Above our window is a shelf, on which I placed my small plastic robot. For the prototype, I connected my phone charger to my headphones with a crude knot, and connected one end to the fan and the other to the robot (this was replaced with a length of white cotton for the finished version). When the fan was turned on, the rotation pulled the string taut, causing the robot to fall from the shelf and be yanked violently about the room.
As you can probably imagine, the path of the robot is highly unpredictable. It seems to work better if the fan is turned on, then off for a couple of seconds, then back on again. This causes epicycles in the circular movement it takes on, making it less likely to smash everything on the mantelpiece.
In the (crappy) picture above you can see the window, the shelf, the robot (circled), the fan, and if you’re particularly observant, the string. I might upload a video of the contraption in action, too, so keep an eye out!