The Apple Watch offers the closest connection yet between your app and users. But you can't just port your existing iPhone app to the watch; instead, you'll write a WatchKit Extension. Learn which of your app's features should come to the watch, how to make your UI look great on both watch sizes with WatchKit's Interface Controller, and how to submit your app to the App Store and get it onto the wrists of your customers. With the Apple Watch, your app is right there on your user's wrist. This book teaches you how to extend your existing iPhone app with a WatchKit Extension, giving your users quick access to your app's most important features and an intimate user experience that's always within arm's reach. You'll learn how to display beautiful interfaces to the user, how to use the iPhone app for heavy number-crunching, and the best way to keep everything in sync across your users' devices. You'll develop a watch app to take advantage of the best WatchKit has to offer, and by the end of this book, you'll be ready to ship your own apps to the App Store. Plus, this book will help focus your efforts.

What features make sense on the watch? How should you organize them? How do you tell your users what they can do? You'll learn how to brainstorm to come up with the best strategy for your app. When your users are proudly showing off their Apple Watch, this book will help you make sure it's your app on there. What You Need: You'll need a Mac running Xcode 6.2 or higher, and for deploying your app to a real watch, you'll need an Apple Watch and compatible iPhone. You'll also need a membership in Apple's developer program to do any on-device testing.