An interaction design agency called Tangible have designed the Zygote, a large 1.5m ball that floats and changes colour depending on the physical interaction within the enviroment. Punching, kicking and throwing it, will make the LED's change colour. It would be great to have them reactive to sound too, but until then, check out the video below. Skip to 2mins in to see the Zygotes being used at a gig.
Check out http://www.tangibleinteraction.com