You're nuts. Walking is, technically, a completely green resource. We're doing it anyway, so why not get additional energy out of it? As for shirts that harness our heat? Bring it on. Again, we're creating that heat anyway, depending on where we live at least half the time without wanting it. Lower your AC bill AND charge your phone!
For non-phone devices already in you, such as a pacemaker, this is a no-brainer.