Seems much easier and accurate to have the supervisors install an app on their mobile phones that checks whether the phones move (and thus being carried by a pe

Seems much easier and accurate to have the supervisors install an app on their mobile phones that checks whether the phones move (and thus being carried by a person) via accelerometer and whether they are on the factory floor via wi-fi/bluetooth beacons and reports to a central server. In general, it's much better to not use machine learning at all if at all possible.