The new Nearby feature is officially continuing to roll out for Pokémon GO via the Adventure Sync functionality. This feature allows players to find nearby Pokémon even while the app is closed. It is now live in multiple regions across the globe, including the U.S., Canada, the UK and other parts of Europe. Read on below to learn more:
Enable Adventure Sync: Nearby
Adventure Sync can find nearby new Pokémon even while Pokémon GO is closed!
Pokémon Blog 