In any disaster event, people need to communicate to ask for help or offer helps. In a worse scenario, let us assume that ISP provider is also affected by a disaster, hence, peoples phone will not able to communicate with other people because the service that interconnect two or more phone is not there. The cellphone is a common gadget today and we use it for communication. How about adding some function on it that phone can act the way the old walkie-talkie works.
1 - Wikipedia contributors. (2018, December 28). Walkie-talkie. In Wikipedia, The Free Encyclopedia. Retrieved 23:49, December 28, 2018, from https://en.wikipedia.org/w/index.php?title=Walkie-talkie&oldid=875726846