Chapter 11
Getting Personal with Sensor Data and HealthKit

Now that you’ve seen the amazing things the Apple Watch can do with touch input, let’s go even further. Touching the screen is an important way that users interact with apps, but it’s not the only one. In this chapter, we’ll look at two more ways that the watch can get data from the user: from its motions through three-dimensional space as recorded by its accelerometer and from the heart rate monitor on the back of the watch. These methods combined can bring an app from a flat, two-dimensional screen to the real world. When you combine the heart rate sensor with HealthKit, an app can become even more: an integral part of your users’ lives. As we explore the heart rate sensor, you’ll add it to TapALap to bring your running app to the next level. To begin this exploration of the world outside the screen, let’s start by using the watch’s accelerometer data to manipulate onscreen content.