Players can unlock the feature by hitting level five, and features that makes use of it will send you push notifications when certain milestones are achieved. This includes moments, such as when an egg has accrued enough steps to hatch.
In addition, there will also be weekly milestones for you to achieve. So, in addition to the standard bonuses tied to your physical activity, there’s the chance that you’ll gain something extra for your efforts. Even if it’s passively earned. The feature can be accessed from the Settings menu. But you’ll have to link Pokémon Go to either Apple Health or Google Fit app first. (Source: Niantic [1], [2])