Ulysses is an interesting long form tool for Mac and the iPad. For me, it falls somewhere between a traditional text editor and Scrivener. I'm currently using it to write one of the two field guides I’ve got in development (Yes. Two.) and I've been pretty happy with the experience.
Today Ulysses’ developers, The Soulmen, announced they’re working on an iPhone version along with some iPad Pro tweaks to their already excellent iPad version. They’ve already announced that when complete, it will be a universal version and they’re looking for beta testers so now’s your chance.