MRI’s are still plenty dangerous when they aren’t scanning(“on”). The magnets don’t ever turn off unless you release all the helium which is typically a last resort. They can do it slowly for servicing but it’s costly or rapidly for emergencies but it usually trashes things.

Seems like the simplest solution is having a locking observation booth. Family can watch from the booth or go to the waiting room. This doesn’t prevent staff from responding to anything and actually keeps the family out of the way if there is an emergency. No high tech gizmos required. Are they go to like it? Probably not. Then off to the waiting room.