Nokia has been running a long and public series of tests of solar-powered mobile charging technology, and the results are in. It really doesn't work very well.
Nokia's test involved sending prototype mobiles with solar-charging back panels on them out to various parts of the world, ranging from Kenya to deep within the Arctic Circle, to gain data from a wide as possible number of use scenarios. But even in the best-case situations, the panels on the back of the unit were barely able to keep a phone alive in standby mode.
If you're happy to move your mobile throughout the day so it tracks the sun or even store it in a holder on your neck (!) you may be able to keep it alive on solar power alone and make the occasional call. But Nokia's overall conclusion is that there's "still some way to go" before solar panels -- and our lifestyles -- suit self-charging phones. [Nokia via TechEye]