It’s true. A device developed by engineers at the University of Wisconsin was capable of transforming the movements that we make while walking into 20 watts (10 watts per foot). This mechanical energy, which is produced both by the movement and by the impact on the ground, would be enough to charge a mobile phone, for example.
In fact there are already prototypes of shoes with a charging device that is fed by the movement of the feet, to which a device can be connected: a phone or an iPod, for example. This would be a very useful tool for mountaineers or runners, for example, who would no longer have to worry about the GPS battery going flat or finding themselves without music from the iPod in the middle of their route.