In reply to BoaseF:
> I'm very sure that if I was lost up in the mountains,I would not be too concerned about privacy.
It's not a privacy problem. So far as I'm aware for now at least remotely piloted aircraft (other than under strictly licenced trial conditions) still legally have to remain within sight of a human spotter to avoid potential conflict with other airspace users. Useless if you want to throw a UAV (or several) out into a rain lashed night to run an automated search grid over a wide area.
Personally I think the obsession with quad/hex copters is a bit myopic in this role, if you want to cover a lot of ground then a fast, efficient fixed wing platform is better and there's volume in the wings for antennae. The problem is safe recovery in bad conditions but there are options. Combine the search/route planning software with a highly detailed local forecasting tool and in most hill regions you can massively extend sortie time by exploiting the hill lift and avoiding the sink.
jk