Niantic has announced a brand-new feature called Adventure Sync for Pokémon GO. With this new feature, players will be able to hatch Eggs and collect Candy, even when Pokémon GO is idle. 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. Adventure Sync will also deliver a weekly summary, where you can see your Incubator and Candy progress as well as important activity statistics. Check in via your Trainer Profile to see the number of kilometers recorded for the week. Earn rewards each week for each milestone you cross, and receive push notifications when your Buddy Pokémon has found a Candy or when an Egg is about to hatch. You can opt into Adventure Sync at any time, and the feature will connect to both Apple Health on Apple devices and Google Fit on Android devices. According to Niantic, Adventure Sync will be available soon.
Source: Official Pokémon GO blog