Apple filed a new patent recently for a multitouch casing on their devices. This rumor has been around for a while starting with the multitouch bezel rumor.
"For instance, holding an iPad-style tablet with one hand could trigger the slate to activate the sensors on the other side of the hardware, so that only the controlling hand can use them. Meanwhile on-screen controls could be shifted across accordingly. Smaller devices could use a rear-mounted sensor for navigation, similar to what weve seen with Motorolas BACKFLIP"
This would be a great addition to all sorts of apps and features on the iDevice. Things like adjusting the volume on your device could be done. This would make it easy to do different gestures while your device is in your pocket. I'm sure game developers would have their own take on such a feature.
These patents keep reappearing in different ways, maybe we'll be able to see something of it soon. I'm guessing, iPad 2?
SlashGear