GoTenna Mesh would be another option even though it only does texting. With the mesh network, you can create your own network without using any wifi or cellular networks. goTenna Mesh
There is also Beartooth which I think is a little better. It turns your phone into a 2 way radio by using the Beartooth device to transmit your signal via 900 mhz. It also doesn’t use any cellular networks or wifi either. As long as you have a solar panel and batteries to charge your phones and devices you can use them.
Checkout goTenna. Could be a good option to complement existing cell phone equipment for local communications if the systems go down. goTenna is a MURS radio that support texting via an app loaded on a cell phone. If the cell systems go down you can still have local area comms with goTennas. Good option for family members. http://www.gotenna.com/