Mark Spoonauer at LAPTOP got a nice story at CTIA today when he sat down with French company Wysips. The prototype he saw puts a solar panel -- a transparent solar panel, thin enough to work with touchscreens -- directly atop the screen of a phone, and with enough oomph to charge the phone with light.
The photovoltaic film (less than 100 microns deep) is only in the development phase now, but Wysips is looking forward to working with glass manufacturers (like Corning, makers of the Gorilla Glass that covers the iPhone 4) to integrate the charger film directly into screen glass.
The solar layer will generate power in room light or sunlight; this version will fully charge a phone in about 6 hours of light exposure, with future generations becoming more efficient as the technology matures. Like the plug-in hybrid technology in today's cars, it might not be enough juice to get you cross-country -- but if the solar film is cheap enough, it would certainly provide a power boost when you're away from your charger.