Walking is a Source of Energy that can be Harvested to Power LEDs or Wearables. It may one day Recharge your Smartphone or tablet. Just start running when the Battery goes low on your Phone.
Here is the first page that will interest you – Parasitic Power Shoes Project
“environmental energy sources can begin to replace batteries in certain wearable subsystems. In this spirit, this effort has examined devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power “parasitically” while walking.”
Goal: To develop a rugged piezoelectric shoe insert and complementary conditioning electronics for unobtrusive, parasitic harvesting of the compression energy normally lost while walking