iOS: Ulysses is one of the best writing tools available for Apple devices and today it's finishing off its trilogy with the release of the iPhone version of the app. If you haven't used it before, Ulysses is something like a plain text editor, supercharged. At one end of the spectrum, it's the same type of distraction-free Markdown editor that we've seen hundreds of. On the other, it's a full suite of organisational tools to keep your writing in order. If you've used something like Scrivener before, then you'll be right at home with Ulysses. The new iPhone version is basically just a smaller version of the Mac app, and it's packed in as a universal app with the iPad version, so if you already purchased that, you'll have the iPhone version too.
The iPhone version supports dark and light writing modes, text statistics, writing goals, a number of Markdown tools and photos. The iPhone version (alongside the iPad one) is just as feature-rich as the desktop app, which is a feat in itself. Ulysses is pricey for a mobile app for sure, but if you want to get a taste of how the app works, you can check it out for free on a Mac.
Ulysses ($30.99) [iTunes App Store]