The first subscriber to the app was Auckland Council civil defence committee chairman Michael Goudie. He encouraged Aucklanders to share their updates on emergency information with friends and family via Facebook and Twitter.
An iPhone user can add family and friends to their network and send a "nudge" to see if they are okay as well as update them on the situation.
Auckland Civil Defence controller Clive Manley said the move to embrace smartphone technology - as well as social media networks - would supplement radio and television broadcasts.
Asked whether the system could cope with alerting half a million people, Mr Manley said a simulated test was done though not when the network was under the actual stress of a disaster when systems would go down - for a time.
The advantage of the apps approach was it gave people options to use the computer network or the text network.
"I subscribe to both text and the iPhone one so if the computer [data] system is down, the text warning comes through.
"But if the text system is down, I can still pick things up through wi-fi," he said. Mr Manley said texting technology allowed pockets or slugs of information to go out on the text system without it getting overloaded
Auckland Central MP Nikki Kaye said People in the Auckland region had to learn from the many lessons that had come from the Christchurch earthquakes, the Japan earthquake and tsunami and last year's tornado at Albany.
She urged Aucklanders to take part in the first national ShakeOut earthquake drill at 9.26am next Wednesday.
A launch demonstration of the drill "drop, cover and hold" was given by pupils of Richmond Road School, Ponsonby, helped by NZ Breakers basketball team members Corey Webster, Josh Bloxham and Morgan Natanahira.
Mr Goudie said the latest Colmar Brunton research showed Aucklanders were less likely than the average New Zealanders to be well prepared for a disaster.
Only 10 per cent were fully prepared compared with the national average of 16 per cent.
How to downloadd - free public alerts by smartphone
* iPhone - go to Apple AppStore.
* Android - go to Google Play Android app store.
* Other - open new window in mobile web browser, type in Blinkm.co/acdnz and save to home screen.
Subscribe to SMS service
Text "high" to "5455" for high severity SMS alerts; or text "medium" to "5455" to get medium and high-severity alerts; text "all" to "5455" to get all emergency alerts.
