Forgive my quoting and not substanially adding to it. In a few weeks you'll get to know why:)
After mobile life in 2003, we go now straight to the present, although a lot of what is written here was already there in July 2003 when I was last time in Tokyo (- so long ago). The article is a potpourri of mobile applications. I will focus here on the mobile wallet stuff:

Japan: A Future Mobile Society?

The Mobile Wallet

Train commuters are about to get another benefit, too. What may well be the world’s largest mobile wallet application to date is being launched in early 2006. NTT DoCoMo has joined forces with railway operator JR East to offer a new service that brings i-mode to the JR East’s Suica IC card and enables easy mobile ticketing.

Given that 10 million Suica customers already use the card for ticketing and also payment at restaurants and convenience stores, the market seems set for another transition in the use of mobile phones. And, when they are tired of shopping, they’ll soon be able to call up their medical records by mobile phone, with even X-ray downloads expected in the foreseeable future.