U.S. and Canadian researchers developed a Knee Dynamo contraption that is able to power a mobile phone for 30 minutes from 1 minute of walking.

The scientists mounted a dynamo on an orthopedic knee brace. Similar to hybrid cars the knee dynamo uses the regenerative braking aspect of walking and uses it to generate electric energy.

The current rather bulky knee dynamo generates 13W from walking.
Now if they just invent a fabric that when bent around the knee is generating that much energy I am going to buy it.
See a video and more information of the Knee Dynamo on BCC News.