Tools such as Elgato Stream Deck and Loupedeck, and third-party apps such as ELMC and Beat Sheet can control Ecamm Live.
To configure which apps have permission to control Ecamm Live, simply go to the Ecamm Live Preferences menu, select Remote Control, and use the checkboxes to assign control to your favorite apps and tools. (Entries will show up here automatically as permission is requested.)