Okay so I had an idea a while back, I think I mentioned it in the IRC.
Essentially, it's a piece of exercise equipment (likely an exercise bike), that allows you to select a 'course'. When you select this option, it brings up a map (google maps but obviously it won't be branded), and you can select a start location and an end location. It then alters your senses so that you appear to actually be in that location (anyone else perceiving you can still see you on the bike). This perception accurately represents it's current state (e.g. any cars passing by are actually located there at that point in time), however nobody can see you.
In order for your senses to be brought back to normal, you have to finish the course. Any attempt to veer off the course will have some sort of invisible force pushing you back on the pathway. If you force your way into danger, it causes injuries that would logically happen to you despite not actually being there (e.g. if you veer into a car, you'd have a lot of broken bones and probably be dead if not seriously injured. However the car would not actually be damaged in reality). Additionally, if someone externally removes you from the bike, it would deal serious damage, both physical and psychological (as you'd essentially be lifted off the bike from something you can't see).
Does this sound interesting? I think it's cool but I don't know if there's enough substance to it.