Focus Feature that prevents editing and only shows each letter you type.
The writer sets a word goal for that session. Then it won't let you edit until you've hit the mark. Backspace triggers a buzzer to remind you to go forward not back. Also, it will only show you each letter that you type so you cannot see the previous paragraph, sentence, or word. Extra points if there's a full-screen mode that only shows you a black screen and the letters being typed.