As reported by CNET News, Apple recently filed a patent for touch screen technology that would incorporate solar cells under the surface of devices with capacitive touch panels.

It appears their goal is to use power from external light sources to increase the battery life of mobile devices and media players. Sketches of iPod- and iPad-like devices were specifically depicted in the patent application. Third-party sources are reporting that recent design changes to their touch panel technology could reflect a move in this direction. More specifically, "switching the iPhone's backside substrate to a non-metal surface would clearly open the door for Apple to implement a double-sided solar panel design."

Developments like this and other "power assisted technology" ideas may be hitting the market sooner than we think and could significantly increase the amount of battery life we see from our portable devices.