What about Ruby Motion for iOS? Its commercial ($200 a license) but offers native objective-c compiled from ruby and is based on the open source mac ruby project.

This seems smart as you only have to learn the cocoa framework and you learn a little bit of objective-c. Whats nice if you want to go native and or optimize by writing straight objective-c you are halfway there.

Everything else I have looked at is basically a web browser attempting to be a full app.

I would love to hear if anyone has written an iOS app that is on the app store with it and what there experience has been.