A smartphone mainly for QR codes...

[Praktica]

The  Covid app is not any kind of commercial enterprise it's produced by the NZ Govt.  So yeah it's free.  You'll need an internet connection on the phone of some sort to download it.  

Are you unfamiliar with smartphones ?
I ask because you may need to learn the difference between and DATA and a WIFI connection and how to access them and when you should use one or    the other.

I'm unfamiliar with Smartphones and don't think it's worth getting one just to scan a couple of codes each week. Even if you use the WiFi connection at home to get the Covid app, don't you have to pay for a monthly plan on the phone? So as well as the cost of the phone, I'd also have to pay so much a month to use it for scanning the QR codes - is that right?

Just keep using prepay.