I was looking around for examples of this, and found a very innovative marketing idea for Fitness First in the Netherlands. The agency with the idea is N=5, and the idea is situated at a Rotterdam bus stop.
Unsuspecting bus travellers sit on the bus stop seat, to see their body weight flashed up in bright lights on the advertising board. A little scary, but very clever, and will definitely increase the number of gym users after an embarassing trip home on the bus.