I suppose it theoretically could work like that, however it surely has the potential to create more panic/mayhem than it solves? I reckon (maybe wrongly) it'll only be used for larger scale incidents.Humour me here, as I have no interest / idea how it actually could work.
Say someone is spotted with a gun, sword, crossbow, whatever. And a 999 call goes in.
Just happens to be right next to a mobile phone mast.
Could the emergency beacon be set only for that mast, alerting only those within the twenty or so mile range?