I remember a guy around '97-'98 who was trying to get me involved in his research around giving the impression of movement in VR systems. Electrodes would be applied to the base of your skull and they'd be used to stimulate your cerebellum (or somesuch, I can't recall) which would give you a sense of movement. This was amplified by standing on a gel mat.

Talking with other people, they said that a side effect of this process was that the electrodes kind've hurt, and none of them would do it again.