I'd also point out that I find it much easier to use Apple Pay with the Apple Watch for London transport than with the iPhone. The Apple Watch is already out, so it actually saves steps (to lhrsfo's point), and because authentication happens when you first put the watch on, presumably well before you need to use it for payments, all you have to do is double-press the side button then wave it on the reader-no passcodes or biometrics at the time of payment. I'm now using the watch for transport 100% of the time and it works a treat, no need to have a specific card out in advance or have my wallet out in a busy station.