I just participated in a market research focus group last month. The company that sponsored the research remained anonymous, but they are actively developing a cell phone card/chip that will:
1) serve as cash (debit directly from your checking account)
2) serve as credit (tie in to your CC account)
3) tie in to all your frequent shopper accounts (e.g. grocery, barnes & noble, gas)
4) allow you to transfer funds person to person, cell phone to cell phone
5) allow for ticketless travel
etc.
The tech for this, apparently, is already in place. Purpose of focus group was to determine which features are most important to end-users and how much (if any) customers would be willing to pay for those services.
I'd guess it's coming soon...