Superphil
Dismember
I wonder if you'll be able to buy more than one ticket with your phone, i.e. if your mate decides to give it a go at the last minute, can you buy 2 "tickets". Or, i guess, it depends how much the sign up process involves. It normally takes very little time to sign up for concert tickets, and with more people having mobile internet, might not be too much of an issue anyway.