Sony is developing a video Walkman to compete against Apple's video iPod, it said today (Thursday). It gave few details and did not indicate how the device will be different from its PlayStation Portable unit, a portable game machine that also has the capability of displaying movies and recording music. At a news conference in Tokyo, Sony exec Hiroshi Yoshioka said only, "We are developing a product that handles images, but I cannot make any comment on specific plans."