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How Do I Prepare My Phone for a Protest?
(themarkup.org)
This is a most excellent place for technology news and articles.
Faraday bags work, period, if they are made and used properly. If there's no RF getting in or out, there's no GPS and no checking in with the towers. Inertial navigation doesn't work worth a damn after a little while, and it won't work at all when powered down. Obviously? black tape over the camera lenses unless you're ready to share what they're seeing, and the microphones can listen very well too, it is a phone after all, so bear that in mind.