Great Concept

Its a great concept looking for a great execution. Instead of being a keyboard onto itself, Hemingboard wouldve been better served had it been an extension to an already well-engineered, established and existing keyboard like Fleksy (which, btw, supports add-ons/extensions).

Another option is be an editing keyboard- where the emphasis is less on the actual writing but more on making it easier to edit an already written piece. While the keys should still exist, the emphasis is now on the easier movement of the cursor (think 3D Touch keyboard or Fleksy or Google Keyboard aka Gboard handles cursor) for quick and easy editing.

MikeMansor about Hemingboard: Synonyms,Rhymes,Puns in Your Keyboard, v1.8