I was reading a page on the web about the best 2015 outdoor gear and this GoTenna caught my eye. It looks like you install some software on your mobile device and then the device uses an external antenna that gives you two-way and group text messaging/communication when there is no cellular phone service. Ranges between devices is stated to be as good as 4 mi. away (flat open desert) to 1/3 mi. (city/buildings/high density).
Since we often end up in remote areas where coverage is spotty or non-existent, this is another tool that may prove useful in a limited communication scenario. Thought I'd share the find since it seemed like a novel approach. Coming Summer 2015.