INaturalistIOS is the official iOS app for submitting data to iNaturalist.org.
We've just finished transitioning to cocoapods:
gem install cocoapods, then
You'll also need to copy
config.h and fill in your details.
That should get you set up for local development with the Simulator. If you want to test on actual devices you'll need to get a provisioning profile from Apple and configure the project to use it: https://developer.apple.com/ios/manage/overview/index.action.
Check out our Roadmap for details on where we're doing.