Hemingway - Hemingway App makes your writing bold and clear.
Readwise - Effortlessly rediscover and organize your Kindle highlights
Grammarly - Clear, effective, mistake-free writing everywhere you type.
Clippings.io - Organize the notes you make on your Kindle
Ludwig.guru - Linguistic search engine and contextualized translator. The final solution for your writing doubts!
Klib - Kindle & iBooks Highlights Manager