The new O2 Wallet service is a money transferring option for smartphone users, although it stops short of offering any NFC payment tools at the moment. It's just for giving money to scrounging mates and shopping.
At the moment, O2 Wallet lets users transfer between £1 and £500 to others, which is done via first channeling funds into a specific O2 Wallet account through a bank, pay point or being sent a "Money Message" from another Wallet user. So it's going to be a little bit fiddly.
The mobile apps also include a bar code scanner, which can be used to capture the details of items then pay for them online, plus O2 says NFC support should be coming to the system soon. And you don't have to be an O2 user for it to work, as was the case with the similar Barclays Pingit app that was recently opened up to all bank users.