It will lockout the skin, even if rebooted. You can also press and HOLD the "Valet" button on the exit screen for the power options for when that button is pressed. You can set it, when the valet button is pressed to lock and shut down, lock and hibernate, or lock and standby.
However, I am not sure how to access it with the omnipass software. It has been a long time since I have used it. Can you drag the omnipass cross hairs (Their new password field wizard) over the text field on the DFX lockout screen to set it to enter the code in the text area when you put your finger on the scanner?
If it is a MS scanner, give Enforcers plugin a go for sure.