Day-to-day use
Do my workers have to use their personal smartphone?
It is not mandatory. You cannot require it without an appropriate legal or contractual basis: if needed, provide a clocking station or a work device.
Workers who wish to can use their own phone. For the others, a shared device (a tablet at the entrance, a computer in the workshop) used as a clocking station lets everyone clock in with their personal QR code (or employee number) and their PIN.
Reference : clause 7.4 of the terms and conditions