Why would an iphone sketchbook be useful?

I recently created an iPhone sketchbook for a project I was working on. I needed a quick way to draw up an interface to explain my concept to the software engineers I was using to build my iphone app. I'm a designer at an architecture firm, and not a trained UI guy, so hand sketching iphone ideas comes more natural to me. I quickly discovered that this iPhone sketchbook was extremely useful, but why would an iphone sketchbook be so useful? Enter the bullet points:

• You never have to remeber the iphone size and proportions again. I've drawn it out for you in the sketchbook. I spoke to several iphone app designers about this problem, and I've found that their current soltion to hand sketching accurate iPhone sketches involves a cardboard template. I'm telling you, the sketchbook is easier to se and more accrate than the template.
• Your thoughts are more organized and easier to find. Let's face it, flipping through a sketchbook is still quicker than trudging through a folder structure. Recall ideas quickly. In fact, I'd suggest getting a few sketchbooks; one for each application concept. In terms of organization, the sketchbook offers areas for notes and doodles in the margins that is free and yet controlled in the opposite page. In other words, relevant data is nearby the adjacent iphone screenshot.
• Relevant hash marks provide quick page layouts. I've included a number of the most relevant hash marks at the margins of the iphone screen to help you to remember where the status and navigation bars will be going on your ui.
• The most rapid of rapid prototyping available. The pencil and paper still beats the speed that illustrator, photoshop, or the SDK have in their ability to get the idea rapidly understood.
• The sketchbook offers a great alternative communication tool to developers. A clear workflow diagram and slick ui screen shots are always handy in conveying your idea to the software engineer, but sometimes a series of simple hand sketches can convey the nuances of your iphone app.

As you probably guessed, I'm more excited about this sketchbook than I am my app. It's true to the extent that I found the iPhone sketchbook so useful that I couldn't help but want to tell developers about this product every day.