RunKeeper is an online health & fitness tracking service built on top of the Health Graph.
The Health Graph allows users to keep track of their workouts, nutrition information, sleep and body measurements data, blood glucose levels, and much more in one place. Users can authorize any of the large and growing number of health and fitness partner apps and devices to read and write data to the Health Graph on their behalf. This allows users to see how every aspect of their health correlates to the others.
RunKeeper's Health Graph API provides developers access to all of this Health Graph information including things such as user profiles, fitness activities, nutrition information, and weight information.