Put on headphones, turn up volume, push the button and try to say something. Can you defeat the app and speak clearly?
Speechless replays everything you say with a short delay. This momentarily confuses the brain and disturbs speech. The phenomenon is well-studied and is used in more serious Delay Auditory Feedback (DAF) devices. It was also recently used to create SpeechJammer gun. Give it a try and have fun!