The Adidas 'Vending Machine Treadmill' is a nice treadmill that provides a snack based on the energy exerted by the runner.
These vending machine treadmills were set up in Dubai malls promote the Adidas Boost shoe. When a runner got on the treadmill, it would begin to count the joules a runner would accumulate during a run. The more calories that were burned during the workout session, the higher the amount of joules and of course, the better the snack.
The vending machine was set up literally right in front of the treadmill, which is just like dangling a carrot in front of a horse. Since this gives runners a goal to work towards that is right before their eyes, it's makes for a great reward system.