If you were at this year’s Glastonbury festival, you might have noticed a bunch of people in Orange (that’s the phone company) T-shirts. They were powering their phones with them.

The shirt is simple: a piezoelectric film (the same thing you find in many speakers) generates a current when exposed to sound waves. Orange says it’s 6 watt-hours, which is enough to power a smartphone. To wash the shirt you can take off the piezoelectric sheets.

The shirt responds to about 80 decibels, which Orange's engineers say about what you would get on a busy street. That said, standing in front of loud cars and trucks to keep on powering your phone is proabably not a good idea; the Environmental Protection Agency prescribes a maximum of 70 decibels for continuous exposure to prevent hearing damage, and traffic can get up to 90 decibels.

But even with its limitations, if you just have to share that video of the mosh pit with your friends at home, this is the power supply for you.