Energy Harvesters LLC is developing the patented Walking Charger™, a footwear-integrated personal power source that uses the motion of walking to recharge mobile devices off the grid. Co-founded by Lawrence C. Grumer and Sherry S. Handel, the Boston- and Rochester-linked startup has built footwear-integrated engineering demonstrators and is pursuing applications spanning everyday wear, work boots, recreation and military use. Its technology can also provide power for footwear heaters, GPS locators and health-monitoring devices.