The trial, which is only taking place at the one store, will mean customers can choose their products, scan the barcode through their phone and then directly drop the items into their bags. So, it's bad news for baskets too.
Special weighing scales for fruit and veg will display a barcode which can also be scanned and will then feed the correct price into the app.
When the shop is all done, customers will do one final scan at a terminal near the exit. The app will tot up the total and automatically subtract the amount from a linked card. There will be no need to go through a checkout at all.
The app has been developed by the company's in-house technological innovation division, dubbed WooliesX.
Woolworths head of payments Paul Monnington said customers were pushing the company to make shopping more convenient.
"We believe smartphone technology and mobile payments have the potential to transform the shopping experience for our customers in the future.
"This trial is not only about testing new technology, it's also about seeing how our customers and teams respond to a completely new style of shopping."
Monnington was at pains to point out you could still pay the normal way at Double Bay.
When the trial finishes up, he said the firm will "assess future options" such as a wider rollout.
Without a staff member checking purchases, one question will be how Woolies can prevent shifty customers walking out with goods they haven't paid for.
The chain certainly isn't the first in the world to try out scan and go technology. Amazon has opened a handful of so-called "Amazon Go" stores which use much the same technology that Woolworths is employing.
While China's Alibaba already has a network of supermarkets called Hema where customers can scan their shopping and have it delivered within 30 minutes to their homes.
But Woolies reckons it's the first in Australia to give the technology a whirl.
Already, Woolworths accepts payment by Apple Pay, whereby customers simply wave their phone, which is connected to their payment card, in front of the register. But they still have to put their products through the till.
In July, a Woolies executive told news.com.au they were steadily shrinking the number of cash accepting check-outs in busy stores as customers' embraced digital and card payments.
Woolworths' Metro division managing director Steve Greentree said customers were moving away from physical money.
"In all of our city locations, people are just ambivalent to cash now. They just don't use it so here (at the Woolworths Metro store on Sydney's Pitt St) we have three registers that take cash and that's it; every other self-service is card only, so it's tap and go or Apple pay," he said.
Cashless tills were safer, he said, because they weren't targeted by thieves. With fewer moving parts, they were also less prone to breaking down and without having to store cash and coins, they took up less room. That meant more check-outs per store.
"They're just much more efficient."
