In a new twist on an old variation, I created a non realtime feedback loop by capturing still images of objects taped and/or affixed to a truly flat CRT with a digital camcorder, which i then displayed on said flat CRT in the background while I captured the next still image, repeat, ad infinitum.
Slight movements and changes in shot geometry alter the "tunnel" effect vastly. It always takes a few frames for the feedback loop to catch up what's happening in "reality", and that's exactly the effect I was after.
The last scene thusfar entailed taping a clear mylar bag of ice to said CRT and capturing one image every five seconds while the ice melted.
This version has an alternate soundtrack ; four mono "automatic" synthesizer pieces combined across the stereo spectrum ...