St John is encouraging people who can do CPR to download an app which could save hundreds of lives each year.
The GoodSAM app alerts nearby people when someone's having a cardiac arrest, something which happens about 5 times per day in New Zealand.
If someone with the app can help, it almost doubles the person's survival rate.
At the moment half of the people signed up are ambulance officers, but if you can do CPR you can join too.
Tony Smith is the Deputy Clinical Director of Hato Hone St John and joins us now.
