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An LAPD helicopter claimed to have ID'ed protesters from above and threatened to "come to your house"
(www.motherjones.com)
This is a most excellent place for technology news and articles.
I'm talking about an actual faraday bag, not a foil bag. That, combined with a powered off device keeps you fairly protected. They aren't going to get into your phone if it's powered off.
There's going to be a deviation in usage regardless, it's not providing an alibi. A gap of time when you're not using your device that you normally would be is a marker they look for. They key is keeping them locked out (again, power them off).