Google today has made available the Google Fit SDK in preview form, meaning developers can now start taking a look at the APIs that'll make all the things a little smarter when it comes to our activities.

The gist is that apps will be able to use existing sensors on your phone or watch or whatever, and pipe that information into their apps. If you're wearing an Android Wear watch, it could take use heart-rate info. Or it could use the step count. It could take the overall history and crunch those numbers. And that's just the tip of the iceberg, of course.

To get things going, you'll need to head into the SDK manager and update things, and then get working with the code.

Source: Google Developers blog; More: Google Fit G+ community