Well, the short answer is, as always, "it depends". I am by no stretch an expert on this stuff, but here are my thoughts.

Unless I'm going somewhere really remote, I now almost always carry my iphone when I'm out hiking. I will often turn it off, however. Partly that's an aesthetic choice, since one of the reasons I go out hiking is to get away from ringing phones and whatnot. Also, that saves the batteries for when and if I really need the phone. (If you have your phone on but are in a no service area, the phone will keep trying to ping a tower, which eats up batteries.) If I get in a jam, I can turn the phone on and try to get a signal.

In many cases I would think that in an emergency it would be advantageous to climb high and try to get a signal, provided one can do it safely, and not go too far. Partly this would depend on how likely you think it might be to get a signal. In many areas, just going a few hundred feet up onto a ridge might enable you to get a signal and make a call out. Around Anchorage, I find that if I can get somewhere where I can see the populated areas in the distance I can often get a signal. It is probably not a bad idea to do some experiments around your favorite areas where you like to hike, and see where you can get a cell signal, and where you can't. Then file that info in your mental memory banks for when you might need it.

Which brings up another point. Just recently I heard about some technology that is starting to become available. It seems there are now portable units which can be used to detect cell phones. My limited understanding is that they are small enough to be transported in a vehicle or by helicopter. If you are in an area with no cell coverage but your phone is turned on, SAR teams could fly the area with the unit in a helicopter, and pick up your phone pinging away looking for a tower, and home in it. So if you are in trouble and you think a SAR team might be looking for you, turn your phone on. (All the more reason to save your batteries for when you really need them!)

Yep, Cellphone data spying: It's not just the NSA The technology to find a cellphone in a remote area is out there, but it may not be active in the search & rescue business -- not that it couldn't necessarily be used in SAR. Then again, maybe they are using it but aren't making the capability known. You don't know what you don't know.

We've heard for some time about the CIA using cell phones to track terrorists and kill them with missles launched from drones. "Stingray" sounds about like what I heard described. I don't think it has filtered down too much into the SAR world yet, but I'm sure it will before too long. I have also heard that there has also been some experimentation with using drones for SAR. Technology is definately a two edged sword!

If I ever decide that I need to run from the law, I will try to remember to hide my cell phone on a bus going the opposite direction from where I'm headed!