For years now [1] BEAM style electronics has used energy harvesting as a power source. The idea is to take some source that produces a very small, yet continuous, supply of electricity and use that to charge up a low-leakage capacitor or battery and then use the  power to do a burst of work. Now [2] Advanced Linear Devices have announced an [3] advanced module that does more or less the same thing for powering wireless sensors. This is not all they can power though. Connect a magnet to a spring and attach the spring to a coil and you have an inertial generator, power as you walk. Connect it to a piezo stack and mount this on the chassis of a vehicle and you get power from road noise. One of the most interesting things you can do however is make a thermopile and paint one side black and one side white and the temperature difference will generate electricity which this unit will then turn into usable chunks. The other interesting idea is to attach a small inductor to this harvester and leave it in any built up area, the stray radio waves and magnetic coupling to power lines will give you a free source of power.So could this mean the end for batteries? Could charging your phone in the future just be a mater of leaving it on the window/radiator/ putting it in your pocket or just leaving it on your bed side table?