"Where Is My Phone" is a clever little app designed to help you locate your misplaced iPhone simply by whistling. But I think we can agree that there are better uses for whistle-triggered sound effect playback than finding your phone.
Turning your iPhone into a remote-controlled whoopee cushion is what I had in mind. Little Worlds, the makers of the app, apparently also had it in mind, including more than one variety of fart among the dozen or so sound effects included with the download.
Here's what's going on: "Where is my Phone" listens for your whistle and then plays the sound effect of your choice (or your own recorded soundbite) when it hears it. The makers claim it can recognise you Zip-a-Dee-Doo-Dah-ing from up to 30 metres away, and I had no trouble in activating sirens, explosions and the rest just by whistling on the other side of the room.