That would be phones within 6ft? I expect quite a lot of false-positive if pinging every second during a working day. And remember not everyone has a smart ph

That would be phones within 6ft? I expect quite a lot of false-positive if pinging every second during a working day. And remember not everyone has a smart phone, or cares for one. If people via a hardware widget strapped to them, I imagine that could create some regulatory hang-ups and class-action lawsuits via various state or national laws on information security, and that a lot would refuse to wear it anyway. Or leave it on their desk. Or find other creative ways. This would be true with phones too. No. Wouldn't work.