RingControl is a handy utility for the Android platform that allows you to put your phone into vibrate mode depending on which way you position your phone. This app uses the accelerometer in your phone to determine when you should be in vibrate mode or normal mode.
When you load up the app, the only real options you have are on or off. Once you turn it on, all you need to do is move your phone either face down or upside down and it will enter vibrate mode. The accuracy is pretty sharp and gives you a little margin of error so you're not popping in and out of vibrate.
RingControl gives you an alternate way to switch which mode your Android phone is in. Using the accelerometer to do this is definitely unique and clever. The only issue is that the only way to keep your phone on the ring setting is to have it face up and earpiece up if you keep your phone in your front pocket.