Merlin it's like listening to Hermio It's one of the few things I've felt I could really help out with around here. I'm all for whatever work it takes.
It might, but then by the time we know it's with the wrong person, it may be too late. Wait, what about a verbal command? We could still do the thing where it warms to the touch if someone is sending a message, but the wrong people could say that was anything, even their own body temperature. If they thought it was a message coming through, could we do something where they can say a word or something and get the message from it?