On May 9th, Shimano was granted patent #7042123, a bicycle electrical generator hub. From the description, it appears that energy from the rotation of the wheel will generate power to operate a rear derailleur. By storing power in the hub, this may lessen the need for an extra battery pack to strap on the bike and would extend the life of a charge. Looks like electric gear shifting is a go! Abstract:
"A bicycle gearshift system is mounted on the rear part of the frame of the bicycle. The bicycle gearshift system includes an electrically powered rear derailleur, a rear hub, a charger part, and a gearshift control part. The electrically powered rear derailleur is mounted on the rear part of the frame. The rear hub is also mounted to the rear part of the frame. The rear hub has an electrical generator mechanism that generates electricity through the rotation of the wheel. The charger part is mounted on the rear hub and stores the electrical energy that was generated by the generator part. The gearshift control part is equipped on the electrically powered rear derailleur, where gearshift control of the electrically powered rear derailleur is performed through the energy that is stored in the charger part."
Electronics: the Next Bicycle Frontier