The move comes hot on the heals of strong indications that Softbank, which has just bought the rival Vodafone KK network, is planning to develop the 'iPhone' incorporating iPod functionality in conjunction with Apple. There has still not been any official confirmation of this, but according to Tokyo based market research company, Eurotechnology Japan, the speculation has been around for over a year.

Also, there has been no indication whether Sony Ericsson's deal with KDDI is exclusive or whether the phones will be available to other carriers.

Music downloads to cellphones is a massive market in Japan. Downloads of full songs to mobile devices 'Chaku-Uta-Full' were launched by KDDI on its 2.4 Mbps au 3G network in November 2004 and the one million download mark was passed within 30 days, according to Eurotechnology. The total now stands at nearly 50 million and 90 percent of music downloads in Japan are to cellular phones rather than to PCs.

KDDI's Sony Ericsson 'Walkman' phones will connect direct to KDDI's online music store, Listen Mobile Service (Lismo). The phones will be capable of storing over 600 songs and playing for 30 hours non-stop on a single battery charge.

Walkman phones have been a major contributor to Sony Ericsson's recent results. Announcing its 2005 results earlier this year the company said the highlight of 2005 had been "the global success of Walkman branded music phones such as the W800, W600, W550 and the W900, which have established Sony Ericsson at the forefront of expanding consumer choice in how people enjoy digital music on the move."

By the end of 2005 it had shipped three million units since the first Walkman phone was launched in volume in August2005.

Sony created the portable music industry with the release of the Walkman in the early 80s (the first versions played tape cassettes). It was quickly followed by numerous competitors but the term 'Walkman' became the generic name for such devices. With MP3 players Sony clearly lost that lead to Apple and the iPod, but with MP3 players and mobile phones merging it has the chance to capitalise on the still strong Walkman name to regain the top position.

Apple must surely be keen to see an iPhone out in the market before the Walkman phone gathers any more momentum.