Buzz Clock is a simple, discreet way to tell the time — even when you can't take your phone out of your pocket. In interviews, on first dates, in church, or at school plays, Buzz Clock silently vibrates at set intervals, so you'll always know what time it is.
Available for free from the App Store and the Android Marketplace, Buzz Clock was written for the iPhone by Greg Knauss and ported to Android by Kevin Wang. It is open source.