Develop iOS apps using an iPhone/iPad (with code)
lesscode.co.nz
lesscode.co.nz
I really like the idea of mocking up via more of a scripting language, especially since it's exportable to a real project in Xcode. As a developer, clicking that many times to build a mockup still seems a bit dreadful to me.
Edit: I believe all the apps mentioned here export to Xcode, just specifying a preference for typing vs clicking :)
Does the same, costs the same, and has been updated as recently as this week – unlike Interface, which was last updated in June.
I just picked up Dapp (http://dapp.kerofrog.com.au/) and put together the first screen of an app that's been bouncing around in my head for a couple weeks. It was pretty intuitive and quick to put it together. I also confirmed that Dapp generates all its code client-side, by using the app only in Airplane mode. Looking over the code, I'm not thrilled about the coding style, but it's not bad for auto-generated code.
So I can't speak for Interfaces (I wasn't going to drop $10 on an app that had terrible reviews about the one killer feature I need) but it seems like Dapp is a winner. YMMV.
Also, although I'd rather it was a universal app, having to pay twice is not fatal, but not being able to prototype iPhone apps on the iPad seems like a pretty weird and artificial limitation.
It's not going to be pulled all of a sudden.