The innovative biofuel cells are capable of converting sweat and the pressure from your fingertips into electric energy, which could soon be enough to power smartwatches and other wearables and sensors. In the long term, this invention could also make integrated batteries obsolete.
https://www.notebookcheck.net/The-sweat-from-human-fingertips-could-soon-power-smartwatches-and-other-wearables.551988.0.html