Researchers at MIT developed the Copenhagen Wheel -- an electric motor that they say can attach to almost any bicycle. The team says:

There is no external wiring or bulky battery packs, making it retrofittable into any bike. Inside the hub, we have arranged a motor, 3-speed internal hub gear, batteries, a torque sensor, GPRS and a sensor kit that monitors CO, NOx, noise (db), relative humidity and temperature. In the future, you will be able to spec out your wheel according to your riding habits and needs.

Users can also dock a smartphone to the Copenhagen Wheel to control how much assistance the electric motor provides.

Link via DVICE | Photo: MIT