Swipe on. Swipe off.
The muster list keeps up.
Crew swipe on and off from their own phone. The board, the headcount and every station update the moment they do — so an emergency roll-call starts from a list that is already right.
The muster list is a view, not a document
It is computed from two things: the rotation (who should be aboard) and the swipes (who is). When the two disagree, the board says so — before the drill, not during it.
When the alarm goes, the list is already right
Start the roll-call and every station gets its own list of who should be standing there — the people aboard right now, not everyone on the roster. Tick them off as they arrive. The clock runs from the first tap.