I'll just make a comment, I don't know if BNZ have the same feature or not:-
The ASB banking app allows you to see the balance and what's available without having to login.
You have to register your phone the first time for security. After that tap once on the banking app icon, then once on the quick balance.
They possibly have the fastest phone bank app balance response time.
It also saves wear-and-tear on the phone because there are less taps on the phone screen.