Google has previewed Google Fit software tools so developers can start writing fitness applications for mobile and wearable devices. Google Fit is a back-end set of APIs that Google wants developers to plug into. The tools will allow programs to talk to sensors, record data and share information with other programs or cloud-based fitness services.

According to Google, there are three sets of APIs designed to meet specific developer needs:

• 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 five 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 a 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 data like read, insert, and delete. When an exerciser finishes a run, the running app can query the History API for all locations during the run and show a map.

A final version of Google Fit APIs is expected later this year.

The developer tools will work with Android Wear and the latest preview version of Android L on Nexus devices. The APIs and installation instructions are available on Google Fit's preview page.