When people walk, run, or otherwise move about, they expend energy. Most of the time this energy is simply wasted. But the M2E Power device will let you reclaim some of this kinetic energy and charge a standard battery with it. This means that basically you, (in a late night infomercial announcer's voice) yes you, can power your own portable devices.
The device is strapped to your belt more or less as a pedometer would be, and the action of your walking powers a small generator. The output from the generator is smoothed out and used to charge the battery. You can wear it when you go out for a run or just out doing errands, and it would no doubt be great for hikers. But if you exercise with it, remember the saying, "No Pain, No Charge".