Wanted to chime in. We currently OEM a product to Purell (GOJO) on exactly this concept. Albeit additional hardware is required, we have been extremely successful locating staff and monitoring of dispensers with BLE.

Our goal has been to prevent the spread of infection in hospitals by monitoring hand hygiene compliance.

‘https://www.gojo.com/en/Newsroom/Press-Releases/2019/GOJO-Ex...