An apparatus for generating an electrical power upon an acceleration of the apparatus is provided. The apparatus including: a piezoelectric member having at least a portion thereof formed of a piezoelectric material; and a mass-spring unit having a spring element attached to the piezoelectric material and configured to compress and/or elongate within a predetermined limit, the mass-spring unit further having a mass offset from the piezoelectric material; wherein the mass-spring unit is configured to vibrate within the predetermined limit, upon the acceleration of the apparatus, the vibration applying a cyclic force to the piezoelectric member to generate an output power from the piezoelectric member.