I saw this on Richard Wiseman's Twitter Feed:
"Take the stairs instead of escalators or elevator and feel better" is something you often hear or maybe read in Sunday attachments. Few if any people have followed this advice. Can we get more people to take the stairs over the escalator on a normal day in Stockholm, by making it more fun to take the stairs? The result you see here.
Photos from Mr. Vogelius' flickr stream:
The technical details are a bit fuzzy from the video, but there are lots of ways to accomplish this today.