Should companies create an app that flags if employees comes within 6 ft

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.

It might make sense but the problem is this “6 feet” thing is basically “BS.”

Any virus that spreads thru moisture in the air that you breath and lives on surfaces for days can travel far more than 6 feet [1].

[1] https://www.webmd.com/lung/news/20200414/cdc-covid-19-can-sp...