I've repeatedly wished for a mechanism integrated into a phone that allows displaying one or more documents (e.g. QR codes, tickets, some other form of document to be displayed) while having the phone otherwise locked (in lockdown mode, so a password is required to unlock it). That would make it much safer to display a QR code on your phone without the net effect of having your phone unlocked when going through security.
Until then, I'll continue to print such things out on paper.
Until then, I'll continue to print such things out on paper.