On iPhone, keys and transit cards that integrate with the system level Key and Express Transit systems work when out of battery as long as your phone isn’t intentionally shut down by you beforehand.

I’ve boarded trains and bought items in Japan with a “completely dead” iPhone using the power reserve feature where Express Transit cards remain available. It actually works really well, and means I don’t have much fear using my phone for those things in Japan.

Granted, ID cards aren’t like this, but there’s no reason why a system couldn’t be added for them.