Android: You've silenced your phone because you're in a meeting but don't want to miss an important call. ViBe creates contact-specific vibrations for calls and SMS — so you don't have to bother with pulling out your phone anymore to see who's calling.
Although ViBe isn't as feature-rich as previously mentioned WhoIsIt for Android (it only does calls and SMS, not email too), ViBe is very simple and intuitive to use. It has one purpose, but it does it well.
You select your contact or contacts, choose from 10 distinct patterns, and then you're done. You can also create your own custom pattern and there's a widget for toggling ViBe on or off or to enter silent mode. A few premium vibration patterns are available for purchase as well.
Until Android has contact-specific vibrations baked in like iOS 5 does, ViBe is a handy app to try if your want to "feel who's calling".