There's a website called Raven that does something similar I think

That looks very cool. I'm using Cold Turkey Writer which is sort of similar. But I genuinely want the feature where if you stop writing it eats the words/vowels. That's the level of pressure that gets past the worst, dithery self-doubt for me.

EATS THE VOWELS??? how is it that your desired software feature is my worst hardcore nightmare?

What can I say? Nothing motivates me to stay on task like MILD TERROR.