What-about-no helps you deliver a strong, clear message to someone that you are telling them "NO". By repeating a no message several times, emphasizing it with a video message from a policeman, and then recording a video of the person being told no (which might be used as evidence against them), the What-About-No app is for those times when simply saying "no" does not seem to be getting through.
Use it to end difficult conversations. Just knowing you have the app can bring added confidence the next time you need to tell someone "no".
Use of the app does not create any kind of a binding contract -- but it is an effective way to say NO.
Note: Recording the video of the person being told "no" is only possible in the premium (paid) version.