The UK and Australia have both published the source code for their contact-tracing apps on GitHub <https://www.theregister.co.uk/2020/05/09/coronavirus_tracing_app_source_code/>. And of course a lot of people are going over them with a fine-toothed comb. Some are even suggesting that one for Apple’s platform, for example, might be violating the company’s rules on using Bluetooth while running in the background. It’s hard to see how these apps won’t be a big battery drain anyway. Maybe the NZ government is wise not to make this sort of thing a priority for now.