Android: When it comes to distraction-free writing tools, it seems like desktops have all the phone. While you may not want to do hours of writing on your phone, Monospace gives you the option when you need it.
Monospace, from the same company behind Today Calendar, is a stripped-down text editor. It supports only a few types of formats including bold, italics, bulleted lists, quotes, and headers. You can also sync your documents to Dropbox. Outside of that, there's very little to the editor to get in your way. Combined with Android's relatively new Do Not Disturb mode, you can focus on writing without distraction. Even if you don't want to write on your phone, your tablet can be a great way to help focus.