Source: The Wall Street Journal
quote: Your iPhone will keep track of places you have recently been, as well as how often and when you visited them, in order to learn places that are significant to you. This data is kept solely on your device and won't be sent to Apple without your consent . It will be used to provide you with personalized services, such as predictive traffic routing.
quote: Interestingly, China is concerned about this “security risk” even though Apple claims that the data is only stored on the device (just like Touch ID fingerprint information) and isn’t sent to Apple.