- This paper addresses energy harvesting from biomechanical motions. Such a technique is useful for powering small portable devices, such as wireless phones, music players, and digital assistants. For very low power devices, biomechanical energy may be enough to provide baseload power. In others, such as cell phones (which typically requires up to 3 W), biomechanical energy would recharge batteries for extended use between line charges, or allow for peak just-in-time power. In this paper, we consider several biomechanical motions for power generation. We evaluate actuation methods, including magnetic, piezoelectric, electrostatic, and electrical polymers for various motions in terms of energy, power, mass, and cost. We also discuss the practical issues associated with each, especially in terms of the power electronics required to connect the biomechanical sources to useful loads.