There was a time when Japanese commuters left home in the morning clutching a newspaper and a boxed bento lunch. Today, the list is more elaborate: MP3 player, 3.2-megapixel camera, navigation system, digital TV tuner and Web browser - all squeezed into a palm-sized device that costs about the price of a good sushi meal.
Millions of Japanese also use cellphones to read novels, magazines and office files, to make credit card payments, watch hours of recorded television and even check body fat.