I was in a discussion a few weeks ago with some iPhone Application Developers and it became really apparent that iPhone GUI Design is now more important than ever. (I will also state through experience, that this is true across ALL Mobile Development +) In fact, for the serious iPhone Application Developer you only get one shot on the App Store to get it right or risk bad reviews and no downloads/purchases, so the success of your application will depend on a great user experience.

As an Enterprise Developer, I have never found my projects to have been so cut-throat, as my users are part of the buy-in from management or project sponsors. If you are following structured project management & iterative development, application designs will evolve through usability/design & test phases, with initial input from the ultimate users.

Traditionally the actual GUI design Phase has probably been about 25% of the whole project time, but now with the iPhone and the nature of the beast that is the App Store, the demanding iPhone Users and the cool device itself... Apple and developers in turn, are pushing this initial design phase to about  60%. Apple's definition of the design phase, is that it consists of four sub phases focusing on...

• becoming familiar with the device and the context in which it is used,
• product definition*,
• design & prototype on paper,
• polish & refine to develop an application with a fantastic user experience.

* The product definition is the foundation of the conceptual design, where the developer states the refined feature set and directions for the application. Without this production definition feature creep can occur and there will not be a starting position on the design & prototype stage

Why paper, other than something like PhotoShop or OmniGraffle? For me going back to the traditional 'low tech' way, is a better way to really think through the UI problem and has a great advantage that this can be done anywhere at any time for low/no cost. For another view...as I mentioned in previous articles, I followed the Stanford’s CS193P iPhone Programming class on iTunes, and in one session you would have heard Steve Marmon, in the lecture 'How to build an iPhone App that Doesn’t Suck', discuss the importance of paper prototyping for iPhone App design. I will let you check that out!

For the Paper Phase check out this cool stencil from the folks at the Design Commission. They have produced this stainless steel stencil to assist with the iPhone UI prototyping, brainstorming sessions, flows and interaction techniques, that you will do in your design phase, before you begin coding. As you can see from the website here, it includes all the icons and buttons, that you would expect. Now iPhone Developer's can sketch out iPhone UI prototypes and take them to their development teams, or a selection of beta testers for review sessions.

Personally, I think this stencil is a great aid for the iPhone GUI designer... it looks so cool and makes me want to break out into application design!    I'm going to design some iPhone User Interfaces on the train home tonight.

+ With any Enterprise Mobile Development, the mobile developer will probably be extending a back end system into the mobile arena... with all its device restrictions on speed, memory, data and screen real estate