Shared here for public benefit.
Before going to a protest, demonstrators or observers should note that their cellphones may subject them to surveillance tactics by law enforcement. If your cellphone is on and unsecured, your location can be tracked and your unencrypted communications, such as SMS, may be intercepted. Additionally, police may retrieve your messages and the content of your phone if they take custody of your phone, or later by warrant or subpoena.
I learned this recently: if you have an iPhone, pressing the lock button five times rapidly will lock it so that you need to enter a passcode, not just FaceID. Useful if you think somebody might forcibly use your face to unlock it
Yes, but this will also call emergency services after, I think, ten seconds.
Make sure you cancel that call right away unless you actually need them.