In this TouchDesigner tutorial we look at how we can use audio data and CHOPs to manipulate a wide variety of sketches. This also works with the audiodevicein. As I quickly touch upon in the video - the input can be anything, not just extracted audio data.
In this tutorial we create a component which can detect when objects are on top of each other (colliding). This works for any 2D input with alpha. You could also render a 3D scene and use it there, it just works on the u v axis though.