While I was at the iPhone studio I heard about a useful tool to build functional wireframes for iPhone apps. It’s called Briefs, and they have a strange but memorable logo.
To make a “brief” you basically you write some code, called “BS”, that specifies what your screens will consist of, complete with input elements and actions that go with them. Then you use a command line tool to compile your bs code into a binary .plist file. This can then be delivered to the Briefs iPhone app over the web.
It all looks pretty cool, but the frustrating thing is that the app is not yet available!
It’s meant to be a framework for building quick and simple app prototypes, but I think Apple is a bit concerned that people would take it too far and use it as a framework to build fully functional apps (albeit simple ones).
As a result, there seems to be a hold up with app store approval on this nice idea. I hope the developers can work something out with Apple, I would really like to try my hand at making some briefs!

Oh wow, it just registered in my mind what the icon is – ha!