What would be cool, and I've been meaning to add it in, is to alter the admin "Check" code to do a "LIKE" search for the main webhost, then bring up a pop up window of all found URLs and ID's. The URL would link to the site, the ID would link to the database entry.

Doing something like that on the Add page, would not stop (should not) stop a user from adding a similar page, but should bring up a notice that the following URLs have already been added to the database.