It's a new computer control device called VIRTUALBIKE to interact with Duke Nukem3d using stationary bicycles (or cyclette).
It connects stationary bikes at computers.

VIRTUALBIKE is a special bike pedal (with electronics pick-up inside) that replaces the mouse control device in Duke Nukem.

In short, once you  plugged VIRTUALBIKE into your computer and tighetened the pedal at your stationary bike, you will move the player (Duke) simply  riding the bike.
When you move the bike pedals forward, Duke walks (rides) on, following perfectly the speed movement of your legs; Duke walks bakward as you turn the pedals in the opposite direction.
What you get, is to perform a Duke match with your stationary bike.
Duke direction (left-right) is controlled by two push buttons fixed (velcro) on the handle bar.