Smartwatches have their pros and cons. You can browse the Internet with the flick of a wrist, but at the end of the day, their battery life simply isn’t that great. Since most people aren’t crazy about the idea of charging their watch every night, MIT Technology Review reports that a Bay Area tech startup called Matrix Industries has designed the PowerWatch, a smart timepiece that’s powered by body heat.

The fitness-tracking watch runs on “thermoelectric generator technology.” According to CNET, this is a fancy way of saying that the temperature difference between your body and the watch is used to generate an electric current. Then, a transformer boosts the charge to run the smartwatch’s processor. The watch also contains a small backup battery, which helps it run when you’re not wearing it.

The PowerWatch is akin to a Fitbit, in that it counts your calorie intake and steps, and monitors your sleep. But unlike most fitness trackers, the watch actually gets a boost when you exercise. "When you exercise, your skin gets warmer, so you'll generate more power," Akram Boukai, the co-founder and CEO of Matrix Industries, told CNNMoney. "It's kind of motivational."

The watch is currently available for pre-order on Indiegogo. It costs $129, and is expected to ship in July 2017. Its full retail price after release is expected to be around $170.

[h/t MIT Technology Review]