Using your phone to board an Air New Zealand flight is now incredibly common. In my experience it's not uncommon to find well over 50% of passengers on peak time main trunk jet services using the feature.
If you don't have checked bags there is no need to visit an airport kiosk and print a boarding pass when you arrive at the airport - you can simply check in online from the Air New Zealand mobile app or enter the Koru lounge which will automatically check you in. You can then proceed direct to the gate and scan the 2D barcode in the Air New Zealand mobile app on the gate scanner to board the plane.
Up until now a paper boarding pass has been printed at the gate scanner and was required to be shown to crew as you boarded the aircraft. As of today this is now no longer printed and you can simply show your phone screen to crew as you board the aircraft.
If you are an Air New Zealand mobile app user who frequently travels with no checked luggage it is important to remember that checking in is required by Air New Zealand before you can fly. If you simply turn up at the gate with your phone having not checked in for your flight you could well find yourself classed as a no show and bumped from your flight.