While reading info for the new iPhone (I still doesn't like it...for an user and developer point of view!), I found a very interesting idea : iPhone Stencil Kit
It could help a lot prototyping an app!
For more tools, I found an old post from Thomas Joos very interesting
From comments, I also found this "iPhone-Catalyst" :)
All of this may, of course, be ported to anything else than pittyPhone !