1. An interactive video image based control system comprising: video imaging means for scanning a field of view occupied by a participant and taking successive images of said field of view; first processing means in communication with said video imaging means and converting the images taken by said video imaging means into digital video information; memory means storing digital area of interest information concerning at least one predetermined area of interest within said field of view; second processing means examining said digital area of interest information in said memory means and said digital video information to determine whether at least a portion of any part of said participant is in said at least one area of interest and the proportion of said at least one area of interest occupied by said participant, said processing means generating output signals having magnitudes dependent on the proportion of said at least one area of interest occupied by said participant; and display means to display a superimposed image of said at least one area of interest and a representation of said participant within said field of view, said display means: (i) providing visual feedback to said participant of the location of said participant relative to said at least one area of interest, and (ii) allowing said participant to interact with said one area of interest to modify said output signals.