This idea occurred to me while watching the Live 8 concert on TV, which looked horrible because there's a band playing in front of a big pixellated screen -- the video image on the screen is covered in Moiré effect. If this were a studio recording, the fix would be to use chroma keying to insert the image electronically afterwards, but that's not an option here because the live audience want to see the image too. Instead, how about we have the screen emit UV light (or IR light, maybe flashing at a high rate that cameras can detect or something) that a modified camera can key on? It's only really the wide shot of the stage that needs this doing to it, since the screen doesn't look so bad when zoomed in.