tangentially wrt. "Depending on the country ... need a warrant or court order " - in Ukraine conflict both sides were using cell phone realtime data for tracking opponents. In particular during August incursion at least some Russian paratrooper platoons were tracked and finally hit that way. Young people who grew up having cell phones all around them and they had it with them during the incursion. Gradually both sides have learned at least to turn cell phones off - so far it seems that that is enough, at least no clear indications to the opposite - before entering combat zones.