alt Hacker NewsThis 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.
At a first glance passive RFID would be a perfect match for ride photos, the whole mechanism is ridiculously fast so speed of the ride would not matter much (the technology works at highway speeds just fine) and can work over ~15 meters.
But there are two somewhat significant issues with the radio layer in this application: the geometry of tag antenna is somewhat critical (making it into a band would be problematic) and the back scatter is attenuated by salt water blobs (ie. people) almost perfectly.