It's amazing how much room for improvement there is in the design of even the oldest things. For example, Philips has developed a woodstove that uses a small thermoelectric generator to power a fan that increases the efficiency of the stove and reduces dramatically the amount of smoke produced. Additionally, the generator can be used to provide power for radios or lights.
Philips estimates it could help 300 million families with this. That's a lot of people, way more than everyone in the US.
Reminds me of the hand-cranked laptop, though it tackles a more basic need.