Our smartphones know much more about us than what we’re scrolling through on Instagram. The sensors in iPhone smartphones can measure everything from how many steps we’ve taken in a day to the length of our stride. If you wear an Apple Watch, your phone knows even more, including your heartbeat, respiration rate, and even how much sleep you get each evening.
Developers can use this data in their apps with Apple HealthKit. This data connection allows developers to read health data collected by Apple devic ...