O2 is considering opening up the specifications for its iMode mobile portal to more third-party content providers, which could lead to more mobile internet applications and services being launched.

However, some experts warned that the standard still might not attract enough customers to compete effectively with GSM and 3G-based mobile internet access.

At a roundtable event to announce that its iMode service has reached 250,000 customers after six months of operation, O2's head of content management, Graham Riddell, said that the 150 content providers currently registered have benefited from low start-up costs. This meant they were able to plough more money back into developing their sites and attracting traffic, he said.

"The O2 iMode service is the fastest growing iMode outside of Japan and we're now seeing content providers getting competitive [with one another]," said Riddell. "We're getting people to use the services and it's not just chat and sport but [big online brands] like eBay and Kelkoo too."

Jag Minhas, O2's chief iMode architect, said the firm had discussed plans to allow other content providers to "open up the toolkits" and develop sites for the standard. He added that this could be put into practice by around the end of this year.

"We targeted certain content providers [in the early months] to provide breadth and depth, but quite a lot more want to get onto iMode," Minhas said.

Mark Blowers of analyst firm Butler Group said that price, usability and content are key to take-up of the service. "A quarter of a million [customers] is quite impressive but… I'm worried iMode might have missed it's time,” he said. “[Although] it's fairly user-friendly it's not particularly unique. For it to get to the next level, users have to be able to access any content they want through iMode."

Blowers said that iMode's chance of success might be restricted by being tied to one mobile operator, compared with the millions of GSM and 3G users and the industry-wide support for the coming .mobi top-level domain.

Meanwhile .mobi has announced the “sunrise period” for trademark holders to register associated .mobi domain names will start on 12 June for trademarks registered or applied for before 11 July 2005. The period will last until 21 August.