Apple developers receive iOS 11.1 beta 4 and watchOS 4.1 beta 4
The build number of the iOS 11.1 beta 4 version for developers is 15B92. For the watchOS 4.1 beta for developers, the build number is 15R846. The latter update adds Apple Music to the timepiece, along with the ability to stream radio stations, including Beats1, over LTE.
If you are registered as a developer with Apple, you can pick up iOS 11.1 beta 4 by going to Settings > General > Software Update. The latest iOS 11.1 beta comes just four days after the third beta was released and should be available around the time that the Apple iPhone X is launched on November 3rd.