Cellphone users can shake their phone to feel and hear how full their battery or message inbox is - as if it were a liquid fuel tank. http://www.dcs.gla.ac.uk/~jhw/shoogle/index.html Video: John Williamson, Dynamics and Interaction Group, Glasgow University. A new system developed by Glasgow University uses a phone's speaker and vibrator to make a device feel and sound like it contains liquid when it is running out of power. The same technique can be used to indicate when new messages have arrived, by simulating the sense of balls rattling around inside a box. The user friendly iphone can take this example forward. Well if you got an iphone then you could always add this to the iphone feature wishlist.