We found this Waterwall project on the Sump.org site, and while its an oldie it’s just too funny to pass up.
This project is the logical result from combining my wish to keep them out of my room with their natural fear of water. So far they had proven very hard to teach about my room. This means the solution had to be automated and on guard 24 hours a day. The idea for waterwall was born and now has become real. For entertaining purposes and lack of other use I threw my webcam in to – hopefully – get some nice pictures.
The Waterwall employs an IR intrusion sensor to detect the presence of a cat, which then activates power to a windshield washer pump which sprays water at the cat. This is only half the fun: the device is connected via the parallel port to a computer, running a script which activates a webcam to capture the event for posterity!
The design is an old one, and could be updated using an Arduino communicating with the PC via serial or USB, with a Processing script to control the webcam.