Technologies for energy harvesting from objects in motion are gaining a continuously increasing interest to directly power wearable electronics, sensors, and wireless transmitters. New networks where things will be uniquely identified and interconnected will require key enabling technologies, particularly cheap, flexible generators of renewable energy, conformable to any solid surface, to power independently individual objects and data transmission. Polymer-based nanogenerators (PNGs), capable of converting mechanical energy into electricity, have exact features to fulfill these requirements. This article highlights advances in PNGs with focus on material chemistries and geometrical features, device design strategies, and performances. Representative examples of applications which show large-scale capability are reported. Concluding sections summarize the key challenges and the commercialization perspectives of PNGs for use in real life applications. (C) 2017 Wiley Periodicals, Inc.