Do you remember the wind-up radio? The one that didn't need a battery or other electricity supply because you could wind it up to recharge it? It had a lot of publicity some years ago.
Now, amongst other things, the Freeplay Foundation produces a portable energy source, the Freecharge Weza. It generates energy by step action, though it can also be recharged from a wind turbine or solar panel.
As reported in the Freeplay newsletter, Wezas have provided a means for Rwandan women to lift themselves out of poverty. They live in areas where there is no electricity so people will pay to have their mobile phones recharged, and this allows the women to buy basic goods they could never afford previously, such as soap and clothes. There are various lighting systems, lanterns and flashlights available too, and can be rented out to generate further income. They all use wind-up energy.
The loan taken out for starting up is repaid out of earnings, and the money can then be used to help other enterprises in the area.