Currently this is only a basic SEO auditing tool, mainly on-site factors. I built this last night using PHP & WordPress as my starting point. Going to make this much more sophisticated over time, and the goal is to keep it free. Think of this version as a bare-bones "On-Site SEO Auditor", it's a great starting point for SEO work.

Right now it provides the following checks: Current Pagerank, Website URL, Blacklist Records, Website Speed, Domain Name Rating, Homepage Title Rating, Description Rating, Keywords Rating, Rich Content Rating, Image ALT Tags, Image Titles, Title Headers, Robots.txt File, Inbound Links, Outbound Links, DoFollow Links, NoFollow Links.

What else should I check for? Any ideas?

What separates this from the masses?

Not trying to steal your fire -- it's pretty slick for a one-day project. I'm sure that, others like myself, would like to know the difference. :)