Odiferous Area Denial System

Inspired by [2 Fries] fake poo to keep trespassers from using his outdoor hot tub or swimming pool. You could scale this to any outdoor area, but first let's picture the small version around a backyard hot tub.

The tub area is surrounded by what look like propane fueled patio heaters. But instead of propane, they can be set to dispense a small puff of smelly gas - either every few minutes or only when a motion detector notices someone nearby. It would have to disperse and break down in a short time, so the simulated farts would only stink up the immediate area and not upset the neighbours. When you WANT to use the tub, you flip a switch (preferably via remote control that you can trigger from some distance upwind) to turn off the smelly flow. The emitters might even be designed not only to LOOK like propane heaters but also BE propane heaters when set to the right mode - not only to burn off the last of the mercaptans but also for comfortable tubbing in cold weather.