This one is a free online script, but I think it might just scrape the results from the web. Not sure exactly how it works. Not sure it matters. It might be the best to give you more accurate results on what is being seen on the web right now.
Additionally, you'll probably get a better test from here because I believe they query all or a few of the google servers, which is something that you may not be able to do yourself through manual or automated testing.