The chip saves power by making use of motion data from the accelerometer, compass sensors and gyroscope of the device. If the same tasks were handled by the A7 chip itself, it would have to utilize 6 times more processing power. The Maps in iOS 7 also makes use of this motion sensing data to switch – for example, from driving to navigation and vice versa. The iPhone 5s will also use the M7 chip to reduce pinging of Wi-Fi which will also improve battery life.
The Motion Activity can be accessed by going into Settings and then Privacy. This setting can be toggled on for selected apps and works in a similar way to third party apps that ask for permissions to access contacts, messages etc.
Apple also says that M7 knows that an iPhone 5s user is driving, walking and running without relying on the A7 chip. The chip can use this data every day, even when the phone is lying ideal.
For example, Maps switches from driving to walking turn-by-turn navigation if, say, you park and continue on foot. And if your phone hasn’t moved for a while, like when you’re asleep, M7 reduces network pinging to spare your battery.After the device is switched on, the motion data is used by an app that may have been active. All this is done through the CoreMotion API that notifies the M7 chip about the movement of the user.
According to a PR from Apple:
The M7 motion coprocessor continuously measures your motion data, even when the device is asleep, and saves battery life for pedometer or other fitness apps that use the accelerometer all day.Apple also said that the upcoming Nike Move (Nike+Move according to iPhone 5s webpage) app will rely on the M7 chip.