The application is called "fan check". This app will allows you to see who is stalking you(or just generally checking out your profile). Well, now the question is how the app works. The answer is simple the app just compiles data based on the way people react with your profile to find out who your biggest fans are, in their own words.The application just ranks your friends based on their activities on your profile how often they interact with your Facebook wall. Interactions counted include wall posts, comments, likes, gifts and all other public activities items posted on your wall. The application will not count page views or private message or any private data.
So, in normal words it will just show you the top fans of you or you can call it top friends.
Well currently the app is off due to Facebook change of profile timeline. But we are hoping the app will be back soon online. So, don't forget to check back.
Fan Check Website