In the sustainable energy market, Energy Floors, a Netherlands-based firm is trying hard to make its place. They sell products like Sustainable Energy Floor and Sustainable Dance Floor, that convert footsteps into electricity. As soon as anyone steps onto the floor, the tile flexes round about 10mm, and that movement is converted into electricity-15 Watts on average, and up to 25 Watts peak. If the tiles are connected together, 40 to be precise, the network can produce up to 1kW and this is possible due to the modular nature of these tiles.

http://wonderfulengineering.com/now-you-can-generate-electricity-while-you-walk-on-this-floor/

Imagine getting paid to run just for generation of electricity.