If you're attending a large-scale protest, it's likely that the cell-towers (or stingrays) won't be able to handle everyone who is connected anyways, so worth planning to use apps that can chat over P2P WiFi or Bluetooth together with the rest of your friends. This also allows you to continue using Airplane Mode the entire time, while being able to communicate with people nearby.<p>Alternatively, investing in walkie-talkies that have encryption can be worth it as well, but unsure how legal they are around the world, think some countries put restrictions on those so you might have to acquire them while vacationing somewhere else.<p>It's mentioned in the body of the article, but get the feeling most people could miss it: Absolute best idea is to leave your "personal" phone at home! Either get a secondary (burner) phone with nothing useful on it and no real names, or skip out on the phone fully. If you do get a secondary phone, make sure it has a removable battery and keep it out from the phone until you arrive at location and as soon as you move, remove battery again.