Google Fit is Google’s new health initiative. It’s a service that will track all your health metrics — sleep, steps, etc. — and it’s built into the next version of Android which means that Google’s Android platform is getting the same kind of life-metric tracking that Apple’s iOS users are getting in iOS 8 with HealthKit.
It also means that the health devices you’re already using will play nice with the myriad Android devices out there.
And all your health data (in theory) ends up in one place, in one app, rather than spread across a variety of software applications.