I just started trying out Open Site Explorer (http://www.opensiteexplorer.org/) yesterday. So I'm interested to see how your tool compares. A feature I like for the aforementioned tool is the "Linking Root Domains". With regards to your tool I definitely like the sounds of email updates both for my own sites as well as competitors. But so as to not be inundated by emails, it might be nice to choose the option to only be updated when a new "Linking Root Domain" has been found.