American Express have followed up their announcement of Serve in Q1 with details of a US mobile network tie-in. Sprint will carry the application in their Mobile App Store for a number of smartphone devices (including iOS, Android and Windows Phone) to give subscribers to the Serve system.

Serve is a digital payment service that’s more than an Amex credit card, and should allow our flexible friend to deal with Web 2.0 companies such as Paypal and Square. With all the start-ups coming out of the Valley, it’s important for the old faithfuls of Visa, Mastercard and Amex to have “skin in the game” not just to gain market knowledge, but also to be seen to be doing something. It’s far easier to change the course of projects like Serve than it would be to start from scratch in three years time when everyone else has influenced the market and how it will all work for the consumer.

And there’s the volume of transactions in Africa and Asia that stay strictly on mobile phones, and never go near a traditional credit card. As an incumbent, you must make a play for those transactions.

So it’s great to see Amex put everything in practice. I’m sure that numbers are going to be small for some time, but what they learn is going to be far greater than the investment, or the income, in 2011.