My screenshot utility, which you can download here runs from the command line and produces a PNG output of your screen. I look forward to using this tool. It's certainly going to be a lot easier than trying to light the iPhone correctly and avoid reflections while snapping pictures with a digital camera.
Update: My daughter figured out that if you set the iPhone to never sleep and put it into camera mode, you can script it to take screen shots every minute (or five minutes or however long) to take time lapse series of images. We are so going to try this out.
Update 2: Tried it out. Only gets about 4 pictures per minute when in a loop so video is a no-go.