This is how all passive RFID works. It's pretty cool. There's even systems that are both passive and active. For example, as a Disney adult, I'm familiar with their magic bands which do have a battery but also work passively. For tying ride photos automatically to you the battery matters because you're either moving too fast or are too far from the camera for passive to be consistently effective. But for simply using it as payment or a ticket you're pressing the device up against a reader and no matter how old the battery is it'll continue working.