Introducing to you The Copenhagen Wheel, a motor-equipped rear bicycle wheel that can turn an existing human-powered bicycle into an e-bike. As you pedal, the motor kicks in and adds a proportional amount of electrical assistance, with a top speed of 20 mph possible to attain. One charge of the battery is good for a range of up to 30 miles, and mounting the wheel is almost as simple as just taking your existing rear wheel off and replacing it.