Does anyone have this problem?

Our receptionist's desk is outside our office security doors and sometimes she forgets to lock her PC when away from her desk*. We're looking for a simple-to-use RFID / NFC / Bluetooth dongle that will lock her computer if she is out of range for more than say 30s. 

Alternatively, we could put a short timeout on her screen saver (2m?) and use something like a Kinect to use Hello to log back in again. But I think that would be super-annoying.

The desk/PC itself is shared, with other staff covering reception if the normal person is otherwise unavailable.

We're running Windows 10, FWIW, and our office uses standard credit-card style cardax (although what the frequency/system is I'm not sure). We wear them on lanyards around our neck, so it would be difficult to lay it flat on a reader on the desk...

Thoughts?

* Yes, I've suggested to the business that it's a training issue and Win+L is super-easy!