When Apple Pay launches in the UK next month there's a big list of retailers who will be supporting the contactless system, but arguably the biggest partner is going to be Transport for London.
Apple Pay will be compatible on all TfL services across the city, but if you do use it you'd better not let your device die mid-journey.
We asked the Director of Customer Experience for TfL, Shashi Verma, what would happen if the iPhone or Apple Watch you used to clock in died before your reached your destination?
He said, "This is something customers need to be careful about and Apple should communicate this.
"Apple Pay requires battery – you've just got to make sure you can conserve your battery and make sure it doesn't die mid-journey."
You need juice
We'd recommend not using Apple Pay if you know you're going to be out of juice by the end of the trip – opt for a contactless payment card instead - otherwise you're going to trapped the wrong side of the barrier at the other end.
Verma told TechRadar that TfL is looking at other contactless payment services, saying, "We will support any wallet enabled with contactless. We're not just Apple focused, we're keen on everyone coming along with this."
He also confirmed TfL has previously looked into creating an Oyster Card app with contactless payment functionality and it may consider releasing a version in the future.
But the big focus is on getting as many people using contactless payments as possible. Verma said, "We're so excited about this. We launched on buses in 2012 and we launched across the whole network in 2014.
"The results are astounding, there are 18,000 new contactless cards being used every day and four million registered cards with only eight million people in the London population."
"It's all exciting stuff and gives more fuel to more modern and interesting payments on our network."
You'll be able to use Apple Pay on the London transport network from July this year, though an exact date hasn't been revealed by Apple just yet.
Verma confirmed it's just a simple case of tapping on the reader and heading in. He said, "It's indistinguishable to how a contactless card works, just fire up Apple Pay and touch on the reader and it works the same way as a card."
You'll need to use your TouchID fingerprint to get through those gates but we reckon you'll have them with you.
Technology wise the readers are all ready and raring to go from today – if you're registered with Apple Pay in the US you can even use it right now.
Just whatever you do, don't let it die mid-journey!