This smartwatch is powered by body heat

 Wearable technology is handicapped by batteries.

The Apple (AAPL, Tech30) Watch has 18 hours of battery life, and a Fitbit Flex needs to be recharged every five days. Compared to traditional watches with batteries that last for years, smart wrist accessories are excruciatingly limited.

But Bay Area-startup Matrix Industries wants to free us from battery woes. Its first wearable is charged by body heat.

The PowerWatch uses thermoelectrics, a material which converts temperature differences into electricity. On a small scale, it's still a relatively nascent technology, but you'll find it in picnic coolers that plug into your car or seat coolers in luxury vehicles.

Here's how it works: When electron particles are heated and move from the side touching your body to the exposed watch face -- which tends to be cooler -- it creates a voltage difference that generates power. This charges the battery, so you don't need to connect it to a power source.