Remember Milkdrop? We created a VJ interface to control the visuals and actually perform with it. We added support for Spout output so you can directly link the visuals into other software.
Feedback loops! We also added Spout Sprites into the Milkdrop engine and so you can create a feedback loop within the engine. This also means that you can bring any a realtime video feed within the drawing process. Here is a recent experiment with a live webcam (starting @ 15:57).