Quite a few of the 200 new features in iOS 5 are focused on accessibility, to "make it easier for people with mobility, hearing, vision, and cognitive disabilities to get the most from their iOS devices." Apple has long been a front-runner with making their devices easy-to-use for their more challenged users.
Buried in the Accessibility settings of iOS 5 is a custom vibration creator. Users can choose from several vibration patterns, illustrated above, or create your own by tapping on the screen at the desired tempo. Taps patterns are recorded and can be used for your phone's vibration.