The platform, often referred to as the 'radio iPlayer', went live on March 31, 2011 with 157 radio stations, including all the BBC's national and local stations, as well as commercial networks such as Global's Capital and Heart stations, Absolute Radio and GMG's Smooth Radio. More than 310 stations are now available on the service, including many community and student stations.
Radioplayer now attracts seven million unique users each month, according to data from Google Analytics, while official audience figures from RAJAR show that online listener hours increased by 32% in the third quarter of 2011, and 10% in the final three months of last year.
This summer, the new Radioplayer app will launch on Apple's iPhone and handsets running Google Android. Developed by All In Media, the app is said to be "as simple to use as a radio", enabling radio fans to discover new stations and material.
In addition to the mobile apps, Radioplayer said that apps are also being developed for internet-connected television sets, starting with YouView, the BBC-backed set top box venture which will launch later this year.
Capablue has signed up to create the Radioplayer apps for 'Smart TV', including potential future launches on the platforms run by Samsung, LG and Sony.
"Our first year has smashed expectations. We thought we'd have 3m to 4m users, and we've doubled that," said Michael Hill, the managing director of Radioplayer.
"We aimed to focus on computers, but we're now rolling out to mobiles and TVs. And we never dreamed the model would spread beyond the UK."
Marking the first birthday, a major marketing campaign for Radioplayer launched this week across various participating stations, including Absolute Radio, Smooth and Real.
The integrated marketing campaign reminds users that they can access their favourite stations through a PC or laptop.
BBC head of audio and music Tim Davie said: "The success of the Radioplayer shows the value of our strategy to grow the whole sector through partnership. The latest round of innovation will ensure it keeps setting the pace."
Radioplayer chairman Andrew Harrison added: "Radioplayer was launched nearly a year ago in an unprecedented display of industry co-ordination. It has grown steadily during that time to its seven million unique users today.
"Our next steps will be to work on behalf of the industry to take Radioplayer onto new platforms, ensuring radio is well represented in areas such as connected TVs and apps."
Other initiatives on the way include the launch of Radioplayer Worldwide later this month, following demand from people overseas about getting access to access the player.
Radioplayer said that an agreement has already been reached in one country, and licensing deals are progressing in "several more". Any revenues generated from the global service will flow back to UK Radioplayer to keep the cost of development "as low as possible for the UK radio industry".
The radio service is also driving innovation around online radio content by making it easier for stations to bring clips and programmes to listeners via podcast feeds.
Sheffield-based GMedia has implemented the new 'click a clip' feature to Radioplayer, which enables stations to attach short-form clips, as recently favoured by tech start-ups such as Audioboo.