Here's a little gem that I whipped up yesterday to get and set preferences in NSUserDefaults on iOSImpact straight from JavaScript.

Just add the .h and .m files to your Xcode project. Then, in your game code, whenever you need to set or get something, just do something like this:

var settings = new native.UserDefaults();
settings.set('audio_enabled', false);

ig.Sound.enabled = settings.get('audio_enabled');

Download the relevant classes here.