Will be a long time coming to UK...
Saw this kind of thing about ten years ago and I just happened to be working for a major UK mobile phone provider at the time. They also had the ability to send credit to other phones, so that you could top up and then share your credit with friends/family. I suggested that we do something similar to the head of mobile payments. Apparently, to do this in the UK we would have had to have registered as a bank, with all the extra costs/paperwork that entails, which is why nothing happened. The only people that I can see offering something similar in the UK are Barclays with their PingIt app...