And if the disaster is an Electromagnetic Pulse?

[Highlander]

...but surely in a real emergency, when their message is being sent out, there is no reason to respond,... ok,... so they know where the phone is, but if it goes nation wide then they wouldn't have the time or the availability to track everyone.

....and, as BP said, once such a message has been sent out, much of the mobile transmitters will be shut down,.. that happened after the shooting in America [ the two brothers],.. mobile phone wouldn't work.

I dont see a negative here [ yet, open to persuasion ],..on the face of it, it sounds like a good sensible idea

Interesting what you said RS,... I wonder if there are particular threats in the other trail areas?