The idea.
An exercise bike, programmable with assorted "courses," with ironic names based on what world they go to. Whenever someone sets a "course" and peddles it, they will vanish. While they aren't there, people can't sit on the bike, or [DATA EXPUNGED].
The interesting thing comes from what happens to the person on it. They claim to have been teleported onto a real bike which they are peddling at the same speed as they were peddling the exercise bike, in another "world" based on what "course" they had entered. As long as the bike keeps moving it will stay in the other world. Therefore returning is just a matter of slowing down and reappearing. If they fall off the bike, or are told to crash it only the bike comes back.
The list of worlds would be a collaborative document, for example,
Course:
World Characteristics:
Ride Time:
Further Notes:
So, what do you think?