Any technology that enables more people to get out on bicycles is a good one in my book, and the Cadence leg prosthetic gets extra points for giving below-the-knee amputee riders the ability to transfer more of their energy into their pedal stroke than existing prosthetics. The Cadence was designed by student Seth Astle and won the prestigious James Dyson award in 2010

Check out this video, via Grist, the shows the Cadence in action:

You can see sketches and more technical details over at the Cadence James Dyson Awards page.