Are You Following Me Too? Was one of the plainest pages I have seen for any tool. One line describes that the tool will check to see who does not follow you back of the people you follow. Then a link to login. While the login is oAuth, you are basically authorizing them to do something that you are very unsure of. Meaning, without any help, about, images or anything else of substance it is scary to click that login box and authorize them.
But give it a shot, the test account seemed to work fine.
Now I did see the tiny my6solitions link in the bottom left corner, which in turn took me to a site with the top entry saying they have this code working. This was basically a blog site saying they released the code for this project under the MIT license since other sites did the same thing. It also had not been tested under large account followings. So use at your own risk.