Zen Tap is an app which is a very advanced text editor. If you want to improve productivity, make better emails, or any other thing about text editing, then
this app is for you!!! Thanks to this app, you can spell check just about everything you write! You could even change the font size! This app also has 4 customizable key buttons, auto completion, a direct export of email, sms, and safari! This app costs $1.99 and I think it is worth it. A YouTube video is below.
Zen Tap Pro is only on the app store.