I rock emacs 24/7 for all code outside of xcode or android studio (php, phantomjs scripts... anything not java or objectiveCMethodWithAnIncrediblyDescriptiveButEffingLongName), and I've found "calm forest" in the color themes package to be a wonderful general theme. It's a great place to start for building in custom syntax settings for "less supported" languages.
Godspeed on the project, and perhaps if I can get some time to force myself into ob-c in emacs at work, I can help.
How does storyboarding work out, or are you just writing the markup directly?
I'm currently only interested in native code auto completion as good as in XCode where it understands the complete class hierachy and types half the boilerplate for you. For Storyboards or Xibs you'd still need XCode. I've long thought about a nice compiler from a simple text format to xib in order to have better version management capabilities, and it may be reasonable now with layout constraints to implement something like that, but I think storyboards would be best done in XCode.
I'll comment on this thread again once I've shared the objective-c emacs code.
Godspeed on the project, and perhaps if I can get some time to force myself into ob-c in emacs at work, I can help.
How does storyboarding work out, or are you just writing the markup directly?