Here's an intriguing patent highlighted by the patent-following folks at Patently Apple -- it's an idea Apple has registered for a "smart bezel," which would be a part of the touchscreen that worked as a separate display only when you're using that part. In other words, if you just needed to adjust the volume or answer a call on your iPhone, only that part of the display would light up and become useable. This could enable things like developers hooking into an "official" gaming controls layout, or just certain tools in parts of the screen layout, like music controls or phone controls in certain states.
The patent also mentions using other parts of the device for a touch interface, which would clear up some space on the main display for more information, allowing you to see it unblocked by your dirty fingers. There's also a hint at a back-panel touchscreen, where your fingers on the back of the iPad, for example, could make some gestures and control things on the main screen as well. This technology isn't unheard of -- the Xperia Play mobile phone has touch panels on the lower section of the device, and rear touch panels have been seen in various concepts before.
It looks like Apple is messing around with all kinds of touch interfaces. As always, these are only patent filings, not actual implementations, so we'll have to wait and see which of these concepts from Cupertino makes it off the drawing board.