Lachlan Murdoch-backed Australian telecommunications and advertising technology start-up Unlockd has expanded into the US, signing a potentially lucrative deal with one of the country's largest mobile providers Sprint Telecom, including advertising partnerships with Twitter and Yahoo.

The deal will make Unlockd's mobile platform initially available to more than 9 million US customers of Sprint's Boost Mobile brand, as it tries to establish a new business model, where customers can reduce or even remove their mobile bills by watching ads.