Yael Miller’s “Kineticel” concept proposes to put small piezoelectric chargers inside common household furniture and appliances, trading a little extra effort in your endeavor for freeish power. Kineticel chargers in a set of dumbbells could make electricity while you’re working out, while a baby jumper could harness the power of your little man-grub’s playtime jittering. (Finally, a way to extract energy out of babies besides eating them!)
It’s all an on-paper concept right now, but I like that the idea is built around battery chargers instead of batteries. The trick would be to discover the materials and environmental cost of adding chargers to relatively simple items in the first place.