Recently discovered Auteureist, an iPhone app for novel writers. I've only played around with it a little so far, but am impressed. Still haven't had time to go through all the detailed documentation provided on the website. Looks as if the app comes with support from the author, and there are even forums (though still pretty empty).
Not only can you work on your novel(s) using this app, but it looks as though you can also track aspects like characters, location and timeline. The app export via e-mail via plain text file; no special formatting is kept unless you export to Scrivener's multimarkdown format. The only way to import text is cut, copy and paste.
Because of the import/export limitation, I would probably only use Auteureist for short sessions of writing. However, the author is working on a new version; you can see some screenshots in the Auteureist blog.
Auteureist is available for US$5.99 from the iTunes store. To find out more info about this app:
Auteureist on Twitter