Brain Injury considerations
I'm late to the party, but I'd like to add my $0.02, FWIW. I read Doug's threads in full. In all cases, the discussion seems mostly limited to broken bones, which clearly the vast majority of hiking accidents. I'd like to contribute to the discussion and add a few little insights as to what happens in the case of a brain injury. This is first hand experience. This is without the details, just providing the learning I had from this expereince.
First, it's a situation where every minute counts. Since so much of it is internal, the situation can, and often is grave. It is extremely difficult to gauge if this is a mild, medium or severe concussion, or perhaps worse. Of course there are some limited outward signs. In this case, help is hours away.
I'm not going to get into the process of assessment and stabilization. That is fairly well understood by this group. I'd however like to share some of the things that can go wrong and what one can do to prevent them. None of these items is necessarily in any order of response.
WFA training does not really cover much about this, especially when help is hours away. After taking WFA there after, it became very clear to me that WFA First Responder would be vastly superior in these situation.
Consider the case of the victim is WFA trained but nobody else in the crew knows what to do. You can delirious, unconscious or otherwise unable to direct the crew , you may be hosed.
Hypothermia can happen any month of the year, in any condition. Don't underestimate the importance of preventing this. Placing the victim on what looks to be a nice soft mossy ground is one of the worst things you can do. A pad is probably the best solution, but there are other inventive forms of protection. For another day.
In addition to the pad, a reflective blanket, a change out of sweaty or wet clothes (if possible) is helpful. Use jackets as best you can for insulation. If the hypothermia progresses, consider your body next to the victim to gain some external heat.
To preserve cell phone battery life, get a hand warmer and put it next to your phone.
As Doug has previously mentioned, staying in contact with 911 is very important, especially if the partners do not know what to do, or panic. First hand experience tells me that if you party does not know what to do or what not to do, you lose precious time and may inflict more injury.
911 can guide the unprepared in terms of first responder medical activities, most importantly to determine body vitals and communicate them on a regular basis to the 911 medical crew. This, is as important in the first several minutes while the rescue crew, sometimes hours away are getting there. Don't underestimate that you or your untrained (or even trained) crew may panic. Most of us are not called upon to use these skills very often. We don't get the experience of a professional EMT responder. 911 will provide a competent resource which guides you through the response.
A through-hiker came along and he only had Boy Scout training, but he had something more important - A large sheet of instructions about what to do in many injury cases, including head injuries. Especially important when we couldn't get through to 911 for about an hour.
I carry a set of 2 way GMRS high(er) powered radios with me. If in any case me or someone in my party may separate, it's another way to communicate. You might be surprised at how well they work, even with geographic obstructions.
While electronics may be our knee jerk reaction to calling for help, don't forget that low-tech whistle. Summonsing others nearby to assist can be extremely important if someone must hike out.
In my case, even with 30 responders at hand, enough time had passed that the responder team was level headed but freaking out because they knew there was a very good chance I was gonna expire. So much so that the EMT crew visited me in the ICU the next day. Do not underestimate the gravity of a concussion, no matter how seemingly mild. You need to be seen at the ER regardless. It's quite possible your situation can degrade over time.
I hope this helps someone.
Some of the facilities I am in are indeed RF shielded, but I'm sure not all of the ante-rooms where we must leave electronics are in the shielded areas. It is possible that the storage boxes may well be designed to shield in those facilities, I don't know. All the boxes I've seen are quite substantially solid, though I doubt many are grounded as required for a true Faraday cage. Regardless, in every situation when I have mistakenly left the phone on, the battery noticeably drains rapidly, so I've assumed they acted as Faraday cages and the poor cell phone was expending energy trying desperately to get out. 
