The latest version of Pages (version 6.1) and iBooks Author (version 2.0) include support for LaTeX and MathML, this is an interesting addition that will be of interest for many scientists
LaTeX is a high-quality typesetting system; it includes features designed for the production of technical and scientific documentation. LaTeX is the de facto standard for the communication and publication of scientific documents.
I've had a quick look at it here.
There is a listing of software reviews here.
LaTeX is used for the markup and publication of scientific documents, it is particularly popular in mathematics, physics, computer science. I know some chemists use it so I thought I'd mention this resource of Chemistry LaTeX packages. It includes packages for most of the major Chemistry journals.
I've been involved in collaborations to write a couple of papers recently and when I mentioned the trials and tribulations of editing and version control when you have multiple authors someone suggested I look at Overleaf. If you are a LaTex user this looks like a very useful option, there are certainly templates for a number of chemistry journals and based on the description on the website it looks like a pretty impressive way for collaborative writing. It looks like they also support iOS.
There is a free option which would certainly be sufficient to try it out.