Pokémon GO is in the process of being updated to version 0.87.5 for Android and 1.57.5 for iOS devices. Details from our development team:
- Added the all-new AR+ encounter mode for Trainers on ARKit-enabled devices (iPhone 6s or later) running iOS11.
- Improved Pokémon GO Plus responsiveness on devices running iOS 11.
- Various bug fixes and performance updates.
—The Pokémon GO team