The Apple Watch has supported connecting a braille display for a while, but it has not supported certain braille displays, including the APH Chameleon, because they use a protocol called HID, which is also used by Bluetooth keyboards, and WatchOS did not support pairing Bluetooth keyboards, so presumably the Bluetooth HID implementation was not included in WatchOS. However, WatchOS 9 now has the ability to connect to a Bluetooth keyboard, which must mean that Bluetooth HID is supported now. Unfortunately, when I tried to connect my Apple Watch SE to my APH Chameleon, the Chameleon said "device selection failed" and VoiceOver made the braille display disconnect sound immediately after the connect sound. However, this is farther than I had managed to get before with WatchOS 8, where I could not even get the display to pair with the Watch. This is similar to what happens when I try to connect my Chameleon to my ChromeBook or an Android device, so perhaps the Watch thinks it is a Bluetooth keyboard. Hopefully Apple will add support for HID braille displays in the future, since it seems like the foundation is there now.