This is a cool concept and some what apt with the world cup just kicking off, the somewhat boringly named Football Fan Display.
Football Fan Display is a hand-held flexible foam board which is used to digitally display messages of support or criticism to players at live matches. This is done by pressing switches on the back to light up sections on the front to form a number or letter. Groups of fans can communicate with players by using multiple products to spell out messages and thus supplying them with a greater sense of interaction at the venue.
Designed by Ross Hubbard, the Football Fan Display is a concept over at DesignSpotter, interesting to see if it will ever actually come into existence.