As microscale devices, such as wireless microsensors and noninvasive biomedical implants, continue to shrink and incorporate more functions, energy becomes scarce, thereby shortening operation life. Furthermore, the limited volume space available constrains the stored energy available in state-of-the-art microbattery technologies, such as thin-film lithium ion (Li Ion). For long-lasting life, it is, therefore, necessary to replenish continuously the energy consumed by harnessing, storing, and delivering energy from the environment in situ, i.e., in the package, alongside the application electronics. Operation life would ultimately be independent from storage limitations. The proposed self-contained, system-in-package solution is composed of three different energy-harvesting sources (light, vibrations, and thermal gradients) that sustain the system, while a charger stores the harnessed energy into an in-package Li Ion. Since substantially low-power levels are expected, the sensor must minimize energy consumption and the system, therefore, must be power moded into various operational modes to consume power only when necessary. Experimental measurements show how an electrostatic harvester sources nanoscale currents that can supply 1.18 mu W from typical vibrations and, thus, recover the system consumption within 37.3 s.