Mules can hear pretty well. You could probably just yell and they would be able to hear. I've never seen one with a radio anyway, other than a Kawasaki
I installed one in a barn with no power for a guy. I used a deep cell battery ( for a trolling motor) with a solar trickle charge and a cell dialer. He never had any issues. Small,water proof , and portable is gonna make it tough.
There would be quite a "herd thinning" if an EMP ever happens. A lot of people wouldn't be able to handle it and off themselves. Then there are the ones who were not prepared at all and die from lack of water/ food or some marauding thugs. Then there are the marauding thugs who maraud the...