eyetracking package for usability research?

Here's an interesting writeup of using eye tracking software to generate "heat maps" that show where on the screen users spend the majority of their time.

Any leads as to good packages for doing this, without paying through the nose for somebody to come in and run the assessment for you?

http://www.useit.com/eyetracking

You may want to look at this page. It was recommended in another question.