An energy harvesting system for use with the human body may use an eccentrically mounted weight winding a mainspring that drives a mechanical clock mechanism. The mechanical clock mechanism in turn may produce pulses of electricity, for example, through periodic flexing of a piezoelectric or triboelectric material during the regular motion of the mechanical timing mechanism. By remaining in a mechanical rather than electrical domain, improved simplicity and efficiency may be obtained in the generation of regularly spaced uniform pulses.