Does anyone know if there's anything about the unlocking method that requires the model to be 3D-printed?

It seems like you could render the 3D model of the head on a monitor and point the phone's camera at the monitor. If the phone needs to see some sort of parallax change relative to its own motion (from internal sensors), then one could put a 6-DOF tracker onto the phone and use it to update the rendered viewpoint of the head (a form of user perspective rendering).

Such an approach would be quite useful for law enforcement to gain access with much less time waiting for printing.