Great writeup, but I wonder why so much emphasis is put on not 'connected to network' part. It seems like a timed inactivity reboot is a simpler idea than any type of inter-device communication schemes. It's not new either; Grapheneos had this for a while now and the default is 18 hours (and you can set it to 10 minutes) which would be a lot more effective as a countermeasure against data exfiltration tools.
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