An amusing PR gimmick at Smithfield Nocturne last Saturday was this bike-powered mobile phone charger, set up by event sponsors HTC. Thoughtfully, there were bikes (way upmarket Scott road bikes, apparently) to fit all riders.
All you had to do was insert your phone in a slot on the handlebar and then pedal like billy-o for an hour and a half, and your battery would then be right back up to full charge.
All a bit of fun, but of course it's meant to make you think. Things such as, why can't I reverse the wires and power my bike with the mobile phone for an hour and a half?*