It might be too much energy to expect from solar, but it would be cool if street musicians could power their sound systems that way. If you use a sub, electric guitar(s), microphone(s), etc., the whole gear weighs pretty much and you need a kind of cart anyway to drag all this with you. So in addition to storing the gear, such a busking cart could have a large foldable solar blanket stuffed in it as well, the blanket could be mounted on a supporting frame and make a small solar roof over musician(s) while they play.
This wouldn't be a service in the original sense as buskers rely on donations, but it's even cooler that way. It would be very cool for such a solar cart to power a small Dj'ing station and for a busker to be able to play a solar-powered Dj set on the street.