Triboelectric nanogenerators (TENGs) are small devices that convert movement into electricity, and might just be what bring us into an era of energy-harvesting clothes and implants. But could TENGs, even theoretically, give us wearable electronics powered solely by the wearer’s day-to-day body motion? The short answer is yes. New research demonstrates the ability of mechanical energy produced by typical body motions to power a watch or smartphone.