I don't know if this is going to have an easy answer, but it's worth a try..
Would it be possible to have a line (preferably a curve, but a straight line would be fine) connected to two separate objects and have it's width/ angle automatically change while one or both of the objects were moving?
The best example I found was this js test - http://raphaeljs.com/graffle.html . You can drag around the markers and see how the arcs still remain no matter what the distance, and the movement is smooth.
I'm thinking the canvas plugin would be used to create the curves, but not sure as far as motion goes...
Any help would be greatly appreciated