Whee! Gyro and Accelerometer!
One of the coolest features of the iPhone, iPad, and iPod touch is the built-in accelerometer—the tiny device that lets iOS know how the device is being held and if it’s being moved. iOS uses the accelerometer to handle autorotation, and many games use it as a control mechanism. The accelerometer can also be used to detect shakes and other sudden movement. This capability was extended even further with the introduction of the iPhone 4, which was the first iPhone to include a built-in gyroscope to let developers determine the angle at which the device is positioned around each axis. The gyro and accelerometer are now standard fare on all new iPads and iPod touches. In this chapter, we’re going to introduce you to the use of the Core Motion framework to access the gyro and accelerometer values in your application.