The US military has used phones’ on/off state in the Middle Eastern war theaters as an indication of potential terrorist activity. Based on other meta data like the number of hops to a known terrorist phone number (phone number A contacted phone number B which contacted phone number C which has contact with a terrorist’s phone number) and the temporal proximity to (assumed) terrorists switching their phones off and on, you got a terrorist rating. If you were unlucky, you got drone-murdered. I can’t find the exact source but this article[1] describes the practice of drone-murdering potential terrorists, and the Talibans counter-strategy.

[1] https://www.rt.com/news/nsa-drones-civilian-casualties-383/