The program determines the ripeness of a berry by sound. All you need to do is bring the phone closer to the watermelon and tap on the peel. If ripe, a corresponding inscription will appear, no will offer to find the next copy. All settings are reduced to setting the size of the watermelon: Large, Medium, Small. I can't say how exactly this program works, the tests will be on in a few days 🙂 
Install from AppStore
