In my active ATC days (unfortunately many years past now) grabbing the Guard (121.5/243.0) handset and transmitting to aircraft on the ground or in the circuit was a regular, but infrequent occurrence which usually "saved the day", if not the occasional life. As a result, those towers for which I have raised Operational requirements and technical specs in the past 15 years as a consultant, have easily accessible guard TX/Rx facilities.
Not my spec, but even Bonriki AFIS can by one touch on the screen TX on 121.5 and the RX monitor is always on and when the vendor finally gets around to the installation, Cassidy will have the same capability,
MJG