Motion sensors let us monitor the motion of a device through space, such as a rotation, swing, shake, or tilt. The movement may be relative to its immediate environment as is the case when you mimic a steering wheel in a car simulation. In this case, we monitor its motion relative to its own frame of reference or that of the application running on it.

However, the movement may also be relative to the environment surrounding the device, namely the world. An example of the latter is determining absolute speed from inside a moving vehicle. The device may be stationary inside the vehicle, but it is moving with respect to the earth at the same speed as the vehicle itself.

The Android platform lets us monitor the motion of a device using a broad array of sensors—some are hardware-based, such as the gyroscope and accelerometer. Others are software-based or they may be hardware-based but dependent on other hardware sensors. Examples are the rotation vector sensor, the gravity sensor...