Carry at least one mobile phone, or satellite by group, as well as emergency numbers. Although it takes off, a phone can be used in an emergency. Satellite phones have the advantage of having coverage in places where cell phones are not the absence of nearby antennas, and capturing its coverage of communications satellites like the GPS.
In addition, mobile phones for emergency contact participants in the activity if necessary, you should also have walkie-talkies for communication between the guides or guardians of the exit (if any) or members of small groups so economic and real-time. In this case communications must conform to the rules of radio communication.
That is, concise and brief to conserve battery power and time, while avoiding confusion or misunderstandings. To this must be taken into account the standard language as well as ours will be a form of public communication, you can listen to anyone within range of coverage and a device configured to the same radio frequency.
Always carry a map and compass and / or GPS (if possible). Do not rely only on the guides (if available). The more aid for orientation count, the better. For cell phones, many Verizon, AT&T, and T-Mobile new smartphones have GPS apps and technology that could possibly help. Of course, it is clear that no good to wear something that does not know how to use or invest in expensive equipment such as GPS, electronic compasses, etc.., When we will use it only once every few years ?