Ask HN: How to create animated iPhone UI demos?

Some teams go straight from design to development.

With my app, I'd like to go from design to 'animated demo' and THEN to development.

In other words, I'd like to take my single frame UI screens and animate them. To create a realistic 'animated demo video' showing what the final product will look like; complete with iOS style effects (moving screens, button states, etc).

My plan is to get the UI setup in Flash CS5 and then use the timeline, motion tweens, and actionscript to animate a user case study example.

That said, this is my first time tackling an interface animation project like this - so I'm curious - is there a better, easier methodology? Perhaps using other tools?

Any tips or suggestions are appreciated.