(YouTube link)

Craig Turner has a problem with neighborhood cats peeing on his property. They spray the house, doors, car, and worst of all, the air conditioning vents. I would just get a dog (which I did), but Turner constructed a homemade defense that involves cameras, motions sensors, and lots of planning. How successful was it? You'll have to watch the entire video to find out. Warning: urination. -via Metafilter