This paper describes a microscale electromagnetic vibration powered generator that harvests kinetic energy and provides a localised power supply for wireless applications. The generator is as resonant device and therefore the power output depends upon the size of the inertial mass, the frequency and amplitude of the driving vibrations, the maximum available mass displacement and the damping. The electromagnetic generator has been implemented with discrete components and produces 58 mu Wrms at 0.6 ms(-2) acceleration from a fixed frequency of 52 Hz and achieves the highest recorded efficiency to date of 51% for a device of this size. The packaged device is 0.8 cm(3) and weighs 1.6 grams. The energy harvested is sufficient to power a wireless, accelerometer based microsystem. The microsystem is energy aware and will adjust the measurement/transmit duty cycle according to the available energy, this is typically every 3 seconds during normal operation.