This initially sounds like something from Star Trek, but the Human Electric Hybrid Drive is what Stokemonkey calls their electric drive conversion kit for Xtracycle® Sport Utility Bikes.
The Stokemonkey Human Electric Hybrid Drive extends the range and carrying capacity of your Xtracycycle bike. It lets you pedal without motor assistance or resistance, but you cannot use the motor alone because it drives the pedals. The benefit of this arrangement is that as you shift gears normally to regulate your pedal speed, you also keep the motor operating between its most powerful and efficient speeds. As a result, Stokemonkey supports hill-climbing, passenger, cargo, and speed capabilities more like those of small cars than of ordinary bicycles, and of all other assisted bicycles as well.