Members of the Association of Train Operating Companies have all agreed to allow members to adopt a national standard for electronic tickets. The standard will allow tickets to be purchased directly on your mobile phone.
The ticket will consist of a barcode displayed on the phone screen that can be read by a ticket scanner at the train station. The application that powers the service runs on Java and allows you to text the departure station, destination, and credit card CVV code to buy the ticket.
The goal for the train operators is to be able to reduce the need for manned ticket windows, which will reduce how much it costs to operate the network. Security concerns will also need to be addressed after the debacles the Oyster Card system has seen.