iPhone is not the first device using solar power. In May, Dexim presents DCA 19 P-Flip with solar-powered battery and dock for the iPhone 3G and 3GS.
New patent filed by Apple is a touch sensor integrated with a solar panel on the media player.
While the next couple of iPhones may not incorporate solar cells, given the recent patent applications by Apple, it's intuitive to realize that the company is looking to put more and more devices on solar power and eventually include iPhones. According to the patent application for solar cells on portable devices, Apple would completely cover the device in a thin film layer of solar cells, even the display.
Based on the description of Gizmodo, Motorola regarded as a pioneer of solar power on the LCD. Models that make the device more efficient, as it can in any way to get sunlight.
If Apple can coat your iPod or other device with solar panels, it can definitely make great efficiency.