dont waste your money on fancy remote callers, if you want a cheap way to have a remote caller, get yourself an old phone and put an mp3 of a rabbit in distres on it and use it as the ringtone, all you have to do is phone the phone an hey presto instant distresscal, distance is up to you other side of the world if you want, but it would be a long walk to set it up for Old Charlie
Excellent idea Hilux.