Motion coprocessorThe iPhone 5s has an M7 motion coprocessor, which lets you use fitness apps and accessories (like the Nike Fuelband, Jawbone Up, or Fitbit Flex) without sucking the life out of your iPhone's battery, assuming they all update their software for the M7.
Over the long term, the chip could help advance gesture-recognition apps and sophisticated ways for your smartphone to anticipate your needs, or even your mental state, researchers say.