A new product called goTenna lets two or more people create a publicly owned wide area phone network for text messaging.
Even without access to mobile services, the goTenna network will operate as a mesh multi-node peer-to-peer network.
You can visit the GoTenna website, and support the product by purchasing two devices for half price.
“goTenna pairs wirelessly with your smartphone, enabling you to text and share your location with anyone who has the device even if you don’t have service. No towers, routers or satellites required!”