Crispin Porter + Bogusky recently put up the above interactive billboard in New York for Jell-O puddings. The billboard monitors twitter for smiley and sad emoticons to work out an American average. If there are more smiley faces the billboard face is happy, if there are more sad emoticons, then the billboard shows a sad face and randomly gives coupons for Jell-O to the people posting sad emoticons.
For an online version go to http://jellopuddingface.com.