Electricity-Generating Road

I believe this invention is relevant to this topic though it's not about utilization of wasted human energy, it's about utilization of wasted car energy.

For many years scientists and engineers have tried to figure out a way to generate electricity from roads and passing cars. Today, an electricity-generating road is under development in Israel.
Underneath the surface of asphalt, roadway engineers fitted a layer of piezoelectric crystals, which generate an electric current when pressure is applied to them. This would allow the road to capture the energy that a car or truck transfers to the ground when it drives by.

Its developers say that the one-kilometre stretch of road is capable of generating 400 kW of energy, enough to power eight small cars.