"I've got a great idea for an app!"
That's probably a sentiment most of us have uttered at some point over the last few years. But relatively few of us probably have any idea how to turn said concept into an actual app. Martian Craft's Briefs aims to change that by providing a you with the tools you need to prototype your app, taking your idea from "under construction" to "that thing's operational!"
Keep in mind Briefs isn't actually for programming apps--it's not a replacement for Apple's Xcode. In my admittedly short time using it, the software it most reminded me of was actually Keynote: You arrange elements to mock up an iPhone app (or iPad app), deciding what screens you'll need, how you get back and forth between those screens, and even what your app will look like on different iOS devices.
Each app prototype contains one or more timelines, which essentially represent a workflow for a specific iOS device: Your options are an iPhone, an iPhone 5, or an iPad. Each timeline is composed of scenes, which each represent a single app screen, complete with attendant buttons, sliders, text fields, and more. For each of these elements, you can specify what it looks like when disabled, or when a user is actively touching it.
Once you've arranged those elements, you can add actions that allow you to perform transformations on the elements in the scene, or even transition to another scene. Using those transitions, you could easily create a simple walkthrough of the app, complete with basic functionality; you can even make both portrait and landscape versions of each of your scenes.
So, where do you get those elements? Briefs comes with a built-in library containing lots of standard iOS widgets for iPhone and iPad, as well as "blueprint" styles for both iOS devices. But if you're handy with a graphics program (or borrowing graphics from other sources) you can easily add your own custom assets. Briefs also accommodates both Retina and non-Retina displays, letting you specify separate assets depending on the resolution.
More to the point, those custom assets can be exported back from the program, helping simplify the often tricky workflow of communicating ideas between developer and designer.
While you can demo the prototype you create in an iOS simulator on your Mac, Briefs really shines when you use it in conjunction with the free companion Briefscase app on your iPhone or iPad. That's a huge boon to those trying to explain their app concepts; there's no better way to do so than to put your app in someone else's hands. In its most simple form, you can send a Briefs file to someone and have them open it; far cooler, though, is using the BriefsLive feature to display your Briefs file, live, on an iOS device running Briefscase--complete with interactivity. And it takes no more than the touch of a button.
It's also worth noting that the launch of Briefs on the Mac App Store is the end of a long and winding road for developer Rob Rhyne. I first saw a version of Briefs demoed at the C4 conference in Chicago in 2009, where it had been designed to run on the iPhone itself (no Mac app involved). Unfortunately, the project ran afoul of some of Apple's App Store rules, and Rhyne was forced to take it back to the drawing board.
There's no question that Briefs is an ambitious tool, and a professional one--at $200, it's not really targeted at the casual hobbyist. But it fills a very specific niche in design and prototyping, one that is often overlooked in the development process.