This work summarizes the energy generation limits from walking employing a pendulum-based generation system. Self-winding wristwatches have exploited successfully this energy input technique for decades. Pendulum-based planar devices use the rotation to produce energy for inertial generators. Then the oscillations of body motion during locomotion present an opportunity to extract kinetic energy from planar generators. The sinusoidal motion of the center of gravity of the body, on the sagittal and frontal planes, and the limbs swinging are compliant with oscillating devices. Portable biomedical devices can extract energy from everyday walking to extend battery life or decrease battery size. Computer simulations suggest energy availability of 0.05-1.2 mJ on the chest, 0.5-2.5 mJ on the hip and 0.5-41 mJ on the elbow from walking.