Apparently, your excess body heat can power up a smartwatch. That's the Powerwatch X, to be released this 2018 by the Matrix Industries.
Its predecessor, the original PowerWatch, was released last 2016, but had limiting features to qualify as a true smartwatch. The PowerWatch X, however, is an updated version that can support smartphone notifications over Bluetooth. Priced at $249.99, it may seem a little "chunky" compared to other smartwatches, but it's definitely an innovative idea in a world that needs constant recharging.
Other companies are also trying to accomplish this feat with kinetic and solar power charging. We can only hope these efforts will extend to our phones! Who doesn't want true wireless charging?