Researchers at Columbia University have conducted the first exhaustive study into kinetic energy harvesting -- the harvesting of "free" energy from common human activities, such as walking, writing with a pencil, taking a book off a shelf, or opening a door. Surprisingly, except for those living the most sedentary lifestyles, we all move around enough that a kinetic energy harvester -- such as a modified Fitbit or Nike FuelBand -- could sustain a wireless network link with other devices, such as a laptop or smartphone.