It's true apparently Hammer!
Here's a link to some info on it Digitalfear, or just google it, loads of results come up,
motion tracking tutorial
The first half of the tutorial is making a motion tracking suit from ping pong balls and a wet suit, but the second half is about importing it into blender.
The guy has used a poser model to stand in for the actual motion tracked footage but it should work with proper footage apparently.
I also found something elsewhere that mentioned "opencvalgorithm tracking" not sure what that is, probably does what it says I guess!