Using an Apple Watch
An Apple Watch can be used as a remote controller for the app with no additional apps or downloads required. Simply open the teleprompter app on the recording screen, and your watch will magically turn into a remote control (as shown below).

Using your Apple Watch, you can:
The play/pause button in the middle switches the script between scrolling and not scrolling. If you tap this button when the script is scrolling then it will stop scrolling. If you tap it when the script is not scrolling then the script will start scrolling.
When recording video, the play/pause icons on the Apple Watch will be correct. If you use the play/pause button when not recording, the icons will be reversed.
You can also use a Bluetooth remote for controlling the teleprompter app.