I just found out about this project called “You Move You Interact,” described as:

…an interactive installation, where one is supposed to build up a body language dialogue with an artificial system so as to effectively achieve a synchronized performance between the real user’s body and the virtual object itself. The project aims at exploring a spatial sphere, where the user/performer is invited to develop his own creative inspiration based on his own body gestures and movements. [ymyi.org]

Also interesting: It’s done using Processing.