Bluetooth headsets have always been something of a trade-off: the convenience of wireless with the headache of having to recharge them, or having the battery run out in the middle of a call. US manufacturer Plantronics has filed a patent on a solution that harnesses kinetic energy to keep your headset fully charged.
According to New Scientist, a so-called 'energy harvester' consists of 'a small flywheel in a magnetic field that rotates when the head shifts, thus generating current.' In other words, nodding your head could ensure your headset is always-on, powerwise.
Possible downside: the patent application doesn't say how often you have to keep your head moving, although the assumption is that natural head movement will do the trick.