Doesn't matter, they have it on their personal phone. App security is so bad that you pretty much need to virtualize the phone and feed it fake sensor data. The whole idea of unrestricted network access is stupid.
A simple approach is to just ban personal phones while at work. You can forward your number to a work phone while you're on duty, you don't need to carry a personal device with you.
About once a week security folks wander through the offices looking for phones with some type of detector. God help the person who brought their phone in.