Matt Stanton, a recent Carnegie-Mellon University graduate from Richboro, Bucks County, is cofounder of a company that is making power-generating shoe inserts.
With every step, a teensy generator in the heel of the insert sends energy to a device strapped to the walker's ankle.
Afterward, the phone can be plugged into it and start taking on juice.
This energy normally would be lost, so Stanton thinks of it as energy scavenging.
So far, an eight-mile jaunt will provide enough for a full charge, said Stanton, whose Pittsburgh-based company is called SolePower L.L.C. The goal is a full charge in 2 1/2 miles - as much as the average American walks in a day.
Now that he's into it, Stanton is seeing many wearable power generators in the works. "In the next five to 10 years, you're going to see some really cool stuff on the market," he said.