Neat, now how does it do that?
Google spits out approximate matches for any query (you know, 1-10 of about some number). One method would be to parse this from Google’s pages. That’s a kludge though which may break.
A better idea? Use Google’s SOAP interface once again (just as I did for my Google cache utility, and as I will use for my custom search interface). One of the results fields is this value. This can be captured quickly and compared. Part of Google’s appeal for now and some time to come is the fact that it not only has a great and accurate engine, but it supplies all imaginable information to third-parties. That may be it’s saving grace as monsters such as Yahoo! come charging like a bull.