Data from cellphone towers is being used to help the Government make decisions around infrastructure, or plan for emergencies.
The project by Data Ventures, the commercial arm of Statistics NZ, uses information from Spark and Vodafone to show the collective number of people in a location at a given time.
But the Privacy Commissioner says it’s "no Big Brother" and has been involved in ensuring people's data is protected.
"We're obviously looking for any possible leaks or ways that you could connect that aggregated data with individuals," John Edwards said.
“This isn't the start of Big Brother. Big Brother is well on down the road, less in Government than in the private sector, as it happens.
"This is a tentative partnership between the telecommunications sector and the Government to really see whether a trusted agency like Statistics NZ can take this commercial data and turn it into something that's of value to the wider economy."
The data will be used by Government departments or local councils to improve or back up their spending decisions on things like tourism and infrastructure, and even keeping the country safe.
"In emergency planning, the difference between 3am and 3pm is really important too because that could be the difference between 10,000 people being counted, or not," said Drew Broadley, executive director of Data Ventures.
"We get device counts, hourly and to suburb level. We can't see any identifiable features - where they've come from, where they're going to, you just see a count at a point in time."
He said they’re still discussing whether the data should be more widely available.
"At the moment Government is our focus, because there's a few things around ethics. You know, who should use it and what they can use it for?"
Both Spark and Vodafone provide 'opt-out' options, but reiterate that no identifying features are provided - just a total number of mobile devices down to suburb level at any given hour.
Vodafone said in a statement it already uses this data to help plan network upgrades, and that it "believes there are a number of potential public good outcomes from these data insights".
Spark agrees, saying "it will showcase the potential of data-driven decision making for Government organisations".