Music fans have finally been offered a solution to the familiar problem of phone charging at festivals - power shorts.
The hi-tech denim garments have been developed alongside a sleeping bag and are designed to boost battery life by "harvesting" body heat and movement. It would mean festival-goers could charge their mobiles when walking from one stage to another, while dancing or even when asleep.
Developers hope the state-of-the-art "smart fabric" technology will provide a 24-hour source of power for campers at outdoor events.
The Power Pocket prototypes, developed by the University of Southampton and Vodafone UK, are being trialled this summer using two different types of energy - thermal for the sleeping bag and kinetic for the shorts. The Power Shorts and Recharge Sleeping Bag could come into use by the end of the year.
Stephen Beeby, professor of electronic systems at the University of Southampton, said: "We are exploring two specific technologies to charge the Power Pocket: thermoelectrics and kinetic energy harvesting.
"Both represent cutting edge research around smart fabrics and we are looking to integrate these into consumer products, in this case, a sleeping bag and a pair of denim shorts."
Tests show that after a full day of walking and dancing, the "harvesting" material in the Power Shorts will charge a smartphone for more than four hours, Vodafone said. Heat generated during an eight-hour sleep in the Recharge Sleeping Bag adds up to 11 hours to a mobile's battery life, according to the trials.
Christian Cull, of Vodafone UK, said: "Our ambition was to create a practical but exciting solution to the charging-related issues experienced by many at outdoor events.
"We hope that people harness the power in their pocket to keep them chatting, texting, browsing and photographing throughout their entire festival season."
The "smart fabric" technology behind the Power Pocket concept is being unveiled ahead of this weekend's Isle of Wight Festival where headliners include The Killers, Bon Jovi and The Stone Roses.