Overleaf - The online platform for scientific writing. Overleaf is free: start writing now with one click. No sign-up required. Great on your iPad.

Hemingway - Hemingway App makes your writing bold and clear.

TeXworks - The TeXworks project is an effort to build a simple TeX front-end program (working environment)...

Write App - No-distraction writing tool for your productivity.

Archimedes - Archimedes is a LaTeX and Markdown editor designed to make mathematical writing easy.

ProWritingAid - For the smarter writer. A grammar checker, style editor, and writing mentor in one package.