I have been experimenting with the iPhone as part of my creative workflow - I already use a variety of applications to get interesting and creative results out of my iPhone photographs such as Photoshop Mobile and Shakeit Lite - and I wanted to see what the possibilities are for creating a full design using the iPhone as a launchpad.
My first iPhone app in this workflow is Adobe Ideas - a simple vector drawing tool for making notes on photos and creating sketches and proofs of ideas in note form. I'm also a big fan of Shakeit Lite and other 'effects' apps for the iPhone - the camera on a 3GS is not actually all that bad and performs very well in daylight. I really like to use it as a visual journal - I'm not going to take a Canon 1Ds MkIII with me everywhere all the time its simply too bulky. I have started to take a few of these 'digital polaroid' images every day with the intention of making a project out of it at some point.
I enclose below a simple workflow diagram for working with the iPhone and Photoshop CS5: