https://wccftech.com/pokemon-go-will-soon-use-google-fit-data-to-hatch-eggs/

One would think that Pokemon Go would be all but dead after it’s initial hype died out. However, Niantic has done a decent job of keeping the game alive through regular updates and new features. Today, Niantic has announced a new feature called Adventure Sync that’s coming soon to Pokemon Go on iOS and Android which will use Apple Health and Google Fit activity data to credit players with distance travelled in the real world for hatching eggs and earning candy even when Pokemon Go is not running. According to their blog post:

Exploring with Pokémon GO has never been easier with a new feature coming soon! Adventure Sync can record your walking distances even when Pokémon GO isn’t launched, working in the background to tally your distance, earn Candy, and hatch Eggs!