I played around with it. Not worth while at this point. Too many privacy risks (e.g. requires you hand over your phone to police unlocked).
Given the amount of deference courts give to cops, that they are allowed to lie without consequence, you don’t need/want to give them any more tools.
Apple could add an API to wrap apps in guided access automatically … or lock the device on app exit. But that’s not going to happen because they want wallet apps to go though their Apple Wallet APIs
If you’re worried about this keep your id card?