I didn't really know how to describe what I need to do in the subject line, so thanks for clicking anyway. I am filming weightlifters from the side, and I'd like to track the path of the barbell. So I have some footage and I have a tracking point on the end of the barbell, but I can't figure out how to track that point and have Motion leave a line on the screen as the point moves.
What you want to do is use a particle emitter. Apply the Match Move behavior to the emitter and tell the Match Move to use the tracking data from the Analyze Motion behavior that you've already done your tracking in. If you set the Speed value for the emitter to zero, the particles will sit still as the emitter drops them, creating a line effect.
A tutorial that demonstrates a similar effect can be found here.