Apple HealthKit

HealthKit introduced by Apple with iOS 8. This tool is designed for your health data. HealthKit provides a central storage for all your health data, for example sleep data, blood pressure data etc. so with HealthKit you can keep track of your health related parameters. 

Apple also provided an interface application to access your health data that is HealthApp. This application provides you dashboard, graphs etc. to see your data. You can also feed the values in HealthKit Storage for different parameters using HealthApp. The HealthApp comes by default with iOS 8. 

HealthKit data can also be accessed, both read and write, by third party applications. The user will have to grant the permission to the third party application so that it could access the data.

The user can also create an emergency card with important health information which is available from your Lock screen.