The development of a method for efficiently harvesting energy from the human body could enable extraordinary advances in biomedical devices and portable electronics. Being electromechanically coupled, nanopiezoelectrics represent a promising new materials paradigm for scavenging otherwise wasted energy, with the ultimate goal of replacing or augmenting batteries. Of particular interest is developing biomechanical energy nanogenerators that are highly efficient, but with flexible form factors for wearable or implantable applications. This perspective presents an overview of the opportunities, progresses, and challenges in the rapidly accelerating field of nanopiezoelectrics. The combination of new nanomaterial properties, novel assembly strategies, and breakthrough device performance metrics suggests a rich platform for a host of exciting avenues in fundamental research and novel applications.