In a natural (or even man-made) disaster, communication on the ground is crucial for coordinating rescue operations but normal communication technologies like cellphones don't work. That's because a lot of the centralised infrastructure (telco celltowers, power systems) are damaged along with everything else.
After the 2011 Feb quake in Christchurch, my neighbourhood was without cellphone (voice and data) communication for a couple weeks because a collapsing fish-and-chip shop took out the local cell tower. Tragically, a couple people who were in the shop at the time were killed.
For situations like this, technology exists that allows cellphones to talk to each other directly, without the need of a cell tower. There are various projects working on this - the most mature I know is open source: the Serval Project, started by a couple Aussies who, I believe, had helped out on the ground following the devastating Haiti quake. You can install the Serval client (gratis - $0) on any Android phone, and it allows your phone to become part of a "self-organising mesh" of phones also running the Serval software.
If you're within a few hundred meters of others running the software, you join their network and can call and text them - or any other phone within the mesh of connected phones! People can even literally tie a Serval-equipped phone to a kite or balloon or stick it up on a hill overlooking a disaster, and offer far greater mesh network reach. It could be the difference between survival and not for a great many people.
Wouldn't it be great if everyone knew about this and simply had this software on their phones? Of course, telco companies hate this sort of technology, because it removes them from the loop (they can only charge you when you use their cell tower infrastructure) and would probably try to bury any promotion of software like Serval. But wouldn't it be great if Civil Defense encouraged people to install and test out this capability? It would certainly give me piece of mind... Because remember: like the Spanish Inquisition, the next big disaster in NZ will hit when you least expect it.