The premise behind Lola Mensa’s Cargador De Celular is pretty simple: By the time you get back from a morning run, you’ll have enough power stored up to keep your mobile phone charged for the rest of the day.

The charger uses the same technology found inside self-winding wristwatches. With every footfall, you give a little more juice to the internal battery, which in turn will power a phone, or MP3 player, or whatever. The flexible design means no major bunions, should you actually stick this concept into your running shoe someday. [Coroflot via DVICE]