On a few occasions I've climbed trees to get a better view when looking for a critter when the blood trail failed me. I can't recall a time when that worked though...usually a desperation move.
I know that some states don't allow electronics to be used to aid in a hunt. Some innocently break this rule when they call a buddy on the cell phone, "One's headed your way." My son called me about 6-years ago to tell me that very thing. However, I wasn't hunting. My tags were filled and I was sitting in a blind, just enjoying firearms opening day with my grandson while his dad hunted. The deer passed me at 40 yards -- yep a VERY big one. He passed my son's stand about 5 minutes before legal shooting time.
I'm not too concerned about this, again, because the battery life is so brief they aren't very practical.
I see no difference, if used for scouting, than putting out cameras to scout deer or time lapse food plots. As long as one keeps to the air space on their own property, or at least property they have permission to use them.
I don't think they should be used, by the public, on public land.
I like the idea of a CO using them to find poachers in areas they aren't supposed to be, such as refuges.