NFC-based payment systems have been slowly sneaking their way onto smartphones around the world for a while now. Google Wallet, having just recently updated their app to support more card types, seemed like a great idea until carriers started blocking it. It wasn’t all that long ago that MasterCard was unveiling their own mobile and web payment system, geared towards offering benefits to the MasterCard customer base. We’ve seen demonstrations on and off from ISIS, but there’s been no real movement on that system for some time now, despite the wealth of support and interest. Now it looks like Visa is getting ready to roll out an NFC-based payment system, joining the increasingly crowded mobile payment space.During one of the “Postcards from London” videos Visa has done in celebration of the London 2012 Olympics, Visa demonstrated contactless payment on a smartphone. Specifically, Visa’s video demonstrated a purchase being made at one of the many locations in the Olympics that accepts payment with a Samsung Galaxy S3. The smartphone is running a special version of the unreleased Visa PayWave app, which works using the PayWave infrastructure Visa already has with keyfobs and contactless cards. During the video, Visa announced that they will be offering the service in the US by the end of this year, pending some agreements with mobile carriers in the states.There’s no telling how far Visa will get with their deployment at this point. Verizon has blocked everything that isn’t the non-existent ISIS service, and AT&T and T-Mobile both have sketchy relationships with Google Wallet. Some phones are allowed to have it and others aren’t, while Sprint includes Google Wallet with everything they can fit the app on to, which might indicate an exclusivity agreement with Google.Over the next year, these payment operators are going to start offering these services more aggressively, and it will be interesting to see who comes out on top. If it means more of the readers installed at more locations around the world, the user adoption rate would skyrocket.