Personally, I think that folks in those type of jobs, should HAVE to turn in the c-phones or whatever they have when they start their shift, - with no exceptions. With today's communications, if there's a family emergency, (not usually the case really) the company will contact then immediately. Before c-phones etc., that approach worked just fine.
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In fact where I work now, for a defense contractor, NO ONE is allowed to bring a c-phone or ANY device that takes pictures into the building. You can leave it at the receptionists desk, or take back to your car and leave it there. The world hasn't ended, ... and the program works just fine.