I was recently at my bees when the friend who was with me had an anaphylactic reaction. Luckily he is OK now. One of the paramedics who attended gave me details of an app (downloadable for free from Play store or Apple store) developed by
Devon Air Ambulance Trust, but useable all over the country. When you open the app, a map appears with your location marked, and your grid reference at the top. It also has a single red button, which once pressed takes you directly through to the emergency services - and tells them where you are. It even activates a torch if you have that facility on your phone!
http://www.daat.org/blog/2012/10/26/our-iphone-app
Now when I go up to the bees, I have this app open and have the phone in my pocket so I could just press the button if needed. I think this app is brilliant and useful for anyone - but particularly beekeepers who are often out in remote places.