The 'Copenhagen Wheel' works on the concept similar to 'Kinetic Energy Recovery System'. It stores energy each time the rider puts on the brake. It the uses this energy to let the cycle move, so that the rider should save energy and doesn't feel tired. The wheel turns your ordinary bike into a piece of tech, as it gives you a live traffic congestion report plus it can check how many calories you have burnt.
For more details check out this video:

