I found some actual detail on the soon-to-be ubiquitous "Google Heat Map" posted below. The company is called Eyetools, and they can generate these heat maps for any webpage - for under $500.
What a great system. I don't know how it works, but I imagine this could be done completely distributed. You hand out eye-tracking goggles to a few hundred people, and pay them for each page they look at. You collect the data and your fee, and generate reports. Given the reasonable cost, I think it must work something like that.
Now that's an internet business model...