We are used to cameras watching our every move, but what about having your phone tracked when you go to the shops or the CBD?
More and more shopping centres and councils around Australia are already doing it - working out where people are going and how they get there.
Adelaide's Rundle Mall is carefully considering the technology as part of a $30 million redevelopment.
Rundle Mall Management Authority chief executive Ian Darbyshire says if the technology was installed, it would help businesses in the area get more information about customer movements.
"You would be able to see what's entertaining people, where people are staying, what's attracting them," he said.
"Part of the Rundle Mall is we're hoping to use it as an events venue - so if you had an event it would be good to see if people came, whether it held their interest, how long it held their interest and maybe where they went afterwards."
Many online stores have had access to highly specific customer data for years: they can already work out how long you spend on a page, which products you did or did not click on, and how often you visit.
Inhouse Group, the makers of one of the offline tracking products, say they are simply helping brick-and-mortar stores compete online.
Inhouse Group chief executive Clinton House says retailers were after mass data and not information about the movement of certain individuals.
"What we do is all anonymous. It's all aggregated - there is no interest from our clients about any individual's behaviour. It's all about aggregated information," he said.
"By the time [the information] gets to our servers, it's already been anonymised ... so there's no identifiable data on our servers at all."
The reaction at Rundle Mall was mixed.
"As long as you're not doing anything wrong and causing trouble, you're OK," one man said.
"I still think it would be intrusive just tracking my movements around the mall. It probably is going a bit too far," said another.
With the technology you do not get to opt in and you do not have to be connected to a WiFi network.
There are two different approaches to tracking the phones. The Inhouse Group system scans WiFi signals given off by smartphones to pinpoint a customer's location.
Another product from the UK - FootPath by Path Intelligence - intercepts mobile phone network signals.
Neither is able to access any content stored on your phone.
In many cases you do not know the systems are in use, and the product's makers will not reveal their clients.
"We respect our clients' privacy probably as fair to say as much as we do consumers' privacy," Mr House said.
"So right now clients do range from small, up to large, retail around Australia but I'm not able to exactly tell you who they are."
There was a similar response from Path Intelligence.
"I can confirm that we have installations in Australia," chief executive Sharon Biggar said.
"We allow our clients the choice of whether or not they wish to speak with the media about our service."
But the ABC understands the use of technology is set to increase.
Inhouse Group already has 20 businesses using their systems around the country, ranging from shopping centres through to cafe's.
Similar technology is installed but not active at Westfield centres in Sydney's CBD, Melbourne and Brisbane.
AMP Capital Shopping Centres say they have planning underway for similar systems at some of their new developments.
The ABC understands the Path Intelligence product has been used to estimate crowd numbers at major events around the country.
Melbourne used it during New Year's Eve celebrations and the Moomba festival to estimate crowd numbers.
Australia's former privacy commissioner Malcolm Crompton is concerned some retailers could be unknowingly breaking the law by using systems imported from the United States.
"It's really quite possible that they're breaching the Privacy Act," he said.
"And here's one thing all companies in Australia need to be very aware of, and it's that the definition of personal information as often applied in the United States is much narrower than in Australia.
"Very often companies in Australia are simply buying and importing an American technology and [applying it] without thought.
He says the problem has a simple solution.
"It comes down to knowing and willing participation," he said.
"It's an easy issue to solve. It's very easy to tell people that you can be tracked, it's very easy to give you an option to get out of it if that's what you want to do - simply turn off the WiFi."