Just got off a RCI cruise and they have an app for check in, health questions, pic and vax card uploads, communicate with each other without wifi, etc. When we boarded they scanned our barcode on the app and our cards were in the notice slot by our cabin door. Also, we could use the app to watch a Muster Drill video and then went to our muster station where they scanned our code on the app to say we know where the muster station is located and had watched the procedure video. Will be on Dream in Nov and wondering if Carnival has something like this.