A group of PhD students from the Computing Science Department of the University of Glasgow, Scotland have developed a haptic keyboard for Apple's iPhone. Their idea is to substitute the lack of tactile feedback in the touchscreen iPhone by stimulating the fingertips through vibration alerts. This basically means that when you press a button on the virtual keyboard, the phone will respond by vibrating. You can download the iPhone haptic application here
, but it said to be extremely buggy, so use it at your own risk.
source: Google Code