Google Fit is a collection of APIs, says Google, "to store and access activity data from fitness apps and sensors on Android and other devices (like wearables, heart rate monitors or connected scales)".
As long as the user grants permission, their fitness history will be made available for building new features. Google cites the example of a personalised coaching app providing more detailed fitness recommendations.
Angana Ghosh, Product Manager of Google Fit, writes that there are actually three sets of APIs:
- Sensors API provides high-level access to sensors from the device and wearables - so with one API your app can talk to sensors, whether on an Android device or a wearable. So if you're making a running app, you could register it to receive updates from a connected heart rate monitor every 5 seconds during a user’s run and give immediate feedback to the runner on the display.
- Recording API allows apps to register for battery-efficient, cloud-synced background collection of fitness data. For example, a running app could ask to store user’s location so it can map the run later. Once it registers for these data types, collection is done by Fit in the background with no further work needed by the app.
- History API allows operations on the data like read, insert and delete. When the exerciser finishes her run, the running app can query the History API for all locations during the run and show a map.