teehan+lax: "Over the past few months we’ve had to create a few iPhone mock ups for presentations. The problem we’ve encountered is the lack of resources to help us design something efficiently. Up until now we’ve used a nice PSD from 320480.com but we still found ourselves having to build out additional assets or heavily modifying bitmap based buttons and widgets." - If you're a Visio user and you need a UI design tool for the iPhone I'd encourage Chris Roth, Mr. Visio Guy himself, to get to work.
Chris, you could blow this out of the water. Then we need to figure out how to generate the Interface Builder .xib file, and associated handlers. That would be a fun project.
Just having the template for building UI's would be wonderful.