This is an interesting idea in principle. Feng-GUI helps you find out how people see your website, photo or ad and which areas are getting most of the attention.

Feng-GUI simulates human vision during the first 5 seconds of exposure to visuals,
and creates heatmaps based on an algorithm that predicts what a real human would be most likely to look at.
This offers designers, advertisers and creatives, a Pre-testing technology that predicts performance of an image, by analyzing levels of attention, brand effectiveness and placement, as well as breaking down the Flow of Attention.

I'm not sure it's all that useful, and it certainly wouldn't replace usability testing or real click-tracking and eye-tracking. The examples imply that people only look ads and dark, saturated areas of color. Doesn't seem very realistic. Have you tried it? What do you think?