To understand MagicMobile, you need to understand "Express Transit mode", which you'll see under iPhone settings under Wallet & Apple Pay.
This is a new feature from Apple that is being used on mass transit systems all over the world, from China to the UK to the New York subways.
It allows you to use your Apple Watch or iPhone to board a subway WITHOUT turning the device on. Mass transit systems have embraced it, because it will allow people to go through the turnstiles much more quickly.
Also, don't sweat battery life. The system uses only a very small amount of energy. Apple claims on their website that you can still use it for as much as five hours after your iPhone battery is at 0%.
For me, the only question will be latency. I'm going next week, and if they can get it to respond as quickly as a Magic Band, people won't have a problem with switching. Especially when they see it doesn't affect their battery.