These socks have a series of soft silicon tubes lining the heel that lead up to small microbial fuel cells embedded near the ankle. Walking around mechanically pumps urine from a 640 mL bladder through the silicon tubes and into the MFCs where bacterial colonies convert the liquid nutrients into an electrical charge. It's not a lot of power, but was enough in lab trials to wirelessly transmit the phrase "World's First Wearable MFC" every two minutes.
The socks are not yet ready for consumers, mind you. As Heather Luckarift, a researcher at Universal Technology Corporation in Ohio told New Scientist, "It's not clear how you would get the urine directly into this system -- how do you pee into your socks?" Still, once that issue is resolved, these socks could eventually make their way into a variety of applications from military operations to medical treatments. The team published their findings in the journal Bioinspiration & Biomimetics.