Here's an interesting application of the motion tracker: not using a static reference image but an animated/tracked one!
I just thought today: If I can track a scene and model the walls, ground, whatever... I can model whatever!
So I made a rotating plate out of an old CD drive and an old printer chassis and recorded this footage.
It works so much better in a clean sheet of paper! I can't believe how easy is to track the points even with the poor 800x600 resolution of my phone!