I Make projects has an awesome DIY VR Bike simulator. Some PVC, a hacked PS2 controller, the Rockstar game “BULLY” on a projector, and a few parts from the workbench results in a crude but effective “virtual bike
“Using an exercise bike equipped with a few modifications, you can effectively simulate riding your exercise bike in and around the town of Bullworth in the Playstation2 game “BULLY” by Rockstar.
You pedal and steer on the exercise bike, and these actions are mirrored in the game, allowing you to virtually ride your bike in and around the town and surrounding areas in the game, complete with cars and pedestrians sharing the roads and sidewalks with you. The faster you pedal on the exercise bike, the faster you go in the game. This whole method should in theory also work with GTA:San Andreas which also has a similar bike mechanic (but a much larger and more visually varied game world than BULLY has).
This is essentially a custom controller interface to an excercise bike, but in addition to the controls it’s also the positioning of the bike in front of a big screen like a projector (my projector is from Lumenlab) and the choice of a game with a good matching “bike” presentation that really makes this whole greater than the sum of its parts.” Thanks Don! – Link.