Saw this mentioned on one news tonight, there is an app for iOS and Android for Civil Defence starting with Auckland first and I believe will end up nation wide.
The idea is for those who don't listen to the radio or watch TV is that its another way to get information to people.

Big thing that jumps to my mind, after the big christchurch earthquake one of the big things being said at the time was to only use your mobile for text only as voice and I assume data would congest the mobile networks, and given all the power cuts using wi-fi wouldn't be possible.

So to me a good idea but could be a problem during a real emergency like a big quake