O2 is opening up its Litmus applications store to let users collaborate with developers, provide input to mobile apps at an early stage and even potentially get paid for testing apps prior to full release.

Litmus was unveiled in late 2008 as a portal where developers can showcase applications and allow consumers to download them.

O2 will announce at the Mobile World Congress show in Barcelona this week that it is expanding the site to provide greater two-way interaction between developers and those who ultimately use their products.

James Parton, head of Litmus at O2, claimed that there is a lot of interest in apps stores at the moment, but that many new announcements are simply " me-too" launches that provide little differentiation.

"You will see lots of app stores, but about 90 per cent of the content will be the same across them all," he said.

By contrast, O2 Litmus will let developers interact more closely with customers for the first time, enabling them to gain a better insight into what buyers are looking for, according to Parton.

The Litmus web site will have different views for developers and customers. The latter will be able to browse the available applications and decide whether they want to get involved in testing, while forums will enable developers and customers to communicate.

Parton explained that applications on Litmus will be divided into two categories: those in a testing phase, and those in the commercial release phase.

"Unlike retail, customers can get involved at the beginning and influence how a product evolves," he said, adding that Litmus members might also be shaping the future direction of O2's network.

Members participating in tests will be rewarded with a free licence for the application they helped bring to market.

O2 is also partnering with Mob4Hire, a web site that pairs developers with testers around the globe, and enables users to be paid for their participation.

"It operates like an eBay auction. A developer can request x number of testers from Litmus, and auction-style bids take place," said Parton. "If accepted, customers get paid the amount of money they bid for their time. The more tests you do, the more your reputation goes up and the more you can charge. "