This is such a powerful tool for the marketing community and web designers to use to evaluate user engagement and make sure attention is in the right places. What are the distractions? What are the focal points? Are we hitting our objectives? Those are some of the questions you can ask with a tool like this. Of course you can use real data later, but during the design process (pre-development) this is going to be great to make optimizations early on in a cost-effective manner.