When we developed Aeir Talk, an speech pathology app for children with Autism, we locked the setup screen (where parents can customize the cards, pictures, and audio) behind a nondescript "Setup" button in the title bar. When tapped, it does practically nothing: It changes to describe to parents how they can unlock the setup screen: "Press While Holding 'Please'", referring to a button on the other side of the screen that is part of the apps regular function. Compared to other touchable elements in the app, the button provides very little feedback, so kids largely ignore it. The gesture requires two hands, tapping two parts of the screen at the same time, so it's unlikely for children to end up in there by accident. You can see a video of this workflow at http://aeirtalk.com/ .