Brian King wrote a blog post on getting pocket sphinx up and running on iPhone a while back and got a few emails last week asking for help. He was so amazing so he cleaned up the code and made a little library for it:
This should give you a library that statically links the sphinix libraries and a simple API that connects to Audio Queue. It also comes with a test program so you should be able to have a demo up and working very quickly inside of XCode.
The plans are to add to the API to support dynamic language model creation, but the main goal is to get people up and running as soon as possible. He would appreciate any feedback!