For the past ten years or so, I've made it a habit to carry a tiny penlight in my pocket whenever I travel. I wouldn't consider myself a hardcore flashlight enthusiast, but when I was younger I used to collect flashlights of different shapes, sizes and output colors. I still have them, lying somewhere in the house, ready for action in case of a zombie apocalypse.
If you're looking for a small flashlight with enough light output to find objects in the dark but would rather not keep supplying it with batteries, you might be interested in Lumen. It doesn't need any external energy source except your body heat. Ross Zhuravskiy is using Kickstarter to raise funding for his creation, and with 26 days until his initiative closes, he officially surpassed his initial $5,000 goal thanks to 477 backers. So how does it work?
"Lumen has relatively simple work principle - you touch TEG (Thermoelectric Generator) - small ceramic bar that can produce electric current when we provide temperature difference between upper and lower parts of TEG.
In my application difference between temperature of your body (about 98 °F) and environment (at least 82 °F) is enough to generate power for single led. Metal body of Lumen serve as a radiator."Check out the video below to learn more about this eternal flashlight.
[h/t: Geeky Gadgets]