Before you comment, no, I'm not thinking of trying to power my home with an old bicycle and a generator. Though I have thought of it in the past.
Have you noticed the amount of devices nowadays that let you recharge your iPod/mobile on the go? There's heaps of them, mostly solar panels in backpacks or sleaves.
When I saw it spiked my interest in it again.
But what about the other parts of your body?
Anyone got a self-winding watch? Those things use a small half circle weight to spin the winding rod. Now what about rumble packs in mobile phones or Playstation controllers? Thay are the same thing except they are attached to a small motor.
If you used these, you could be making power even when it's overcast.