You can tick off this task if everyone present in sensitive meetings switches off their phones or takes them out of the room.
People who are involved in civil society, conduct investigative research or uncover abuses often have access to particularly sensitive information and deal with particularly vulnerable people or groups. A leak of information through e.g. wiretapping could potentially endanger people.
If you are politically active, you should be particularly careful. Devices belonging to you or your comrades could be infected with malware or be tapped. Switch them off to increase trust in a conversation!
Remember that other people cannot know how well you know your own phone. It is therefore always a sign of mutual trust to keep phones out of sensitive conversations. The general rule should be: Trust people rather than their devices.