Ann Makosinski, a 15-year-old high school junior from Victoria, British Columbia, created a hollow flashlight powered only by the holder's bodily heat, as part of a Google Science Fair. The invention made her one of 15 finalists, who will travel to Mountain View, California for a prize ceremony held this coming September. Google will show 1 winner for 3 different age groups, before deciding on the final winner.
She created the device using the idea of Peltier tiles, which are devices that create energy when one side is heated while the other side is cooled. In total, after struggling with a few hurdles, she needed only $26 to construct her flashlight. Here's her discussing the project.

Via ExtremeTech