I really like this idea. Wear Your Music collects used guitar strings from popular musicians, turns them into bracelets, and sells them, with 100% of the net profits going to the musician's charity of choice. Tony Iommi of Black Sabbath has donated some of his guitar strings, with the proceeds going to Nordoff Robbins music charity. There are several different styles available, at different price points.
Other musicians of note include Robert Trujillo, Kirk Hammett and James Hetford of Metallica; Lita Ford; and David Ellefson of Megadeth.