This DIY project may well be one of the best gags ever for the frequent flatulator in your home. A builder going by the name Schmidtn has designed a remote control that will change the TV to a random channel when it smells a fart.
The builder came up with the idea after seeing an office chair that Tweeted each time it detected a fart and a hack that changed the TV channel using one of those brain wave headsets. This would make a seriously good practical joke.
The supply list includes a methane sensor, Arduino, and some other parts. You can check out the full instructions on Instructables to build your own.