Thinking out loud... an RTL-SDR dongle costs like $35.00 or so (well maybe more now due to tariffs, I haven't bought one in a while), plenty of relevant software is open source (GNURadio etc.), drones are cheap, small solar panels are fairly inexpensive. Hmm... I almost think a motivated individual (or small group of individuals) could piece together a rather capable "distributed monitoring/alert" system.

Not that I'm encouraging anyone to do such a thing, of course.