It appears that people with hidden phones will need to ensure they are shut down for a some time around the AusAlert test on Monday.

They need to be shut down from 1pm Monday until at least 2pm Tuesday:

Ms McBain said people with concealed phones, who may be at risk of domestic violence, can turn them off or put them on aeroplane mode at least an hour ahead of Monday’s test, and for at least 24 hours after.

via ABC News.