In reply to mypyrex:
I think it was 1991 that I was first on a call-out involving a mobile phone in Kintail. A helicopter lifted an injured person from the Forcan Ridge probably less than 2 hours after the incident. In February 2005 in the Cairngorms, the combination of two factors related to radio comms, mobiles phones and personal issue MR radios, meant that within a few minutes of breaking her ankle, a woman was attended by 3 MR guys from 3 different MRT teams, and an hour and a quarter after the incident she was landing at Raigmore Hospital in an RAF helicopter.
Last year, I was on one where there was not mobile phone coverage and the companion had to walk out get help. The difference was clear. I do not know if there was a mobile phone carried at that incident but I do know that if the companion had gone up instead of down there would have been coverage for a 999 roaming call regardless of network. There is nearly always coverage on summits but accidents don't happen on summits.
Things are moving on. MR teams are examining, and some are using successfully, applications that will track lost persons who have contacted them using smart phones (don't expect this to work in the most complex terrain). IKAR members are examining how MR teams can scan ground for a known mobile using specially built equipment and information from the network provider. Some of these new things will work and some will not. Do not expect any of this to be magically available any time soon.
Read the advice on this leaflet.
http://www.outdoorindustriesassociation.co.uk/cust_images/Mountain%20Rescue...
And here are a few more tips.
1. Charge it. Turn stuff off, or down, to extend battery life. Carry a spare battery (charged).
2. Protect the phone from wet conditions. (Tesco ziplock bag?)
3. Understand 999 roaming and its limitations. You can call 999 on any network: not just your own. Problem: you can only be called back on your own network. Solution: get the vital information across clearly in the 999 call, don't waste battery energy with other useless phone activity and arrange a time to call 999 again.
4. POLICE. Don't ask for an ambulance. They don't do hills.
5. SMS text messages can work far better than voice in areas with poor coverage. Have two or three numbers of reliable people who will have their phones always on who can be relied upon to pass on text messages to the police.