Same-sex marriage opponents have launched a phone application giving campaigners "turn by turn" directions to undecided voters' homes, in what it describes as an unprecedented move in Australian political campaigning.

The app was developed by the American company Political Social Media LLC, trading as uCampaign, which built apps for Donald Trump's presidential campaign, Brexit's "Vote Leave" and the powerful National Rifle Association.

Among the features of the "Freedom Team" app, launched Wednesday evening, is a tool that maps the home addresses of people whom the Coalition for Marriage says have not yet engaged with the campaign.

"The app will provide turn by turn directions to your nearest neighbour who is yet to hear from the campaign," the Coalition told supporters in an email. "And it will give you talking points for when you get to the door."