This app allows you to unlock your Galaxy S4 screen by blowing air on it, I just tested it on mine and it works.  You have to blow the air at the top area where the sensors are.  I guess this application works by taking advantage of the Proximity sensors. I found out about this app through one of those Indian blogger’s Google Plus post.   It is an app from one of those unheard of international phones. All that matters is that it works.  Now if only someone can make an app that allows us to answer when we blow air on our screens. Here is download link, it’s called MicroMax Unlock Galaxy s4 blow air to unlock your phone