I interned at VPL Research[1] in 1992 and they had a Mac-based VPL for controlling objects in VR called Body Electric[2] that was really fun to use - especially since I'd never seen anything like it. I implemented gravity for objects and a virtual arm using it. If I remember correctly, debugging could be a challenge. It was later interfaced with Macromedia Director[3] to control desktop apps.

[1] https://en.wikipedia.org/wiki/VPL_Research

[2] http://www.jaronlanier.com/vpl.html

[3] http://www.art.net/~hopkins/Don/lang/bounce/bounce.html