Let me revise my curmudgeonly previous post.
Carrying a GPS is here to stay and there seems to be no stopping it, even though it's bad enough that people don't know how to use a map and compass anymore, now they carry one of these and don't know how to use it. But there's no going back on this one, I fear, and overall it's probably not too bad of an advance.
Carrying your camera as part of a multi-device is probably okay, if that's what you plan on using to take all of the pictures of your trip.
However, I am dead set against listening to music in the backcountry. Whenever I see someone hiking or backpacking along a beautiful trail wearing earphones, with the sound of the wind in the trees, the babbling brook by your side and the birds calling as they swoop through the skies the only thing I can think of is how badly I would like to practice SSS and put them out of their misery.
I don't believe in taking a phone into the backcountry either. Too many unprepared people head out with them as a crutch, calling in a rescue instead of finding a way out of it like the good old days (yes, I am old). If one is really worried about getting help in case of a
serious accident or getting lost, carry a SPOT.
The problem these days, as Benny mentioned as a plus, is that smart phones now have all of this, and more. So, it's getting harder and harder to get people to unplug and enjoy nature as it is, without some electronic enhancement - which is why I am mostly against it on principle.
Smart phones are incredible things. I was reading an article today about the decline of retail, and where are all of the retail jobs going.
http://finance.yahoo.com/news/where-did-retail-jobs-131000931.html They had reposted a picture from a tweet (another piece of crap that shouldn't be allowed to access in the backcountry, btw) and the caption was that all of this now fits in your pocket (meaning smart phones)
I guess I am just an old fart, bemoaning the fact that young people (and some old) now prefer to listen to music in the backcountry rather than the music of nature and are so engrossed in the electronics that they lose sight of the reason that most of us head out anyway - to get away from civilization and all that crap and back to a simpler time in life before we have to return.
Btw, when Ryan swings by next to check out the forum (probably in a few months since he was here recently and FB is so much more interesting) he may comment on his JMT hike and what they did. I know that when they stopped at my place in Mammoth for a night off the trail that they left behind a bunch of batteries that they didn't need. I don't remember if they had a charger, or just weren't burning through them as fast as they thought, or what, but he will probably have something to add here.