It would be incredibly useful to be able to add tracking markers on top of the video which automatically (if possible!) follow objects using pattern recognition and allow us to display the arcs. Frame by frame manual placement of markers would also be useful for difficult-to-track footage.
The only way I've found of tracking arcs currently has been to paint dots with the brush frame by frame and then use ghosting to show something resembling the arcs, but this is not ideal.