It is likely that the reader will be implemented into a phone / tablet app so will be pretty ubiquitous eventually.

FWIW it will never technically be legal to rely on visually looking at someones phone to verify age / id bc it would be incredibly easy to fake the display and physical interaction. The only reason it can work as an ID is if it is digitally verified by a reader.

But I do agree that especially in the interim there will be cases where LEO will coerce a phone handover but I don't think this will be a long term problem since physical interaction with the phone does nothing to verify authenticity. You may as well hand them a piece of paper you printed out with your info.