Accessibility changes
As well as new support for Bluetooth keyboards and new Quick Actions in Assistive Touch, watchOS 9 also introduces a huge new accessibility feature: Apple Watch Mirroring.
This connects your iPhone and your Apple Watch via AirPlay, and it enables you to control the Watch from your iPhone. That means you can take advantage of your iPhone’s accessibility features such as Voice Control and Switch Control.
To enable the mirroring feature, open Settings > Accessibility on your paired iPhone (it won’t work with other iPhones) and then choose Apple Watch Mirroring. A large version of your Apple Watch face will now appear on your iPhone, and it’s fully functional. Anything you do on your iPhone will be mirrored instantly on your Apple Watch and vice-versa.