could you make it possible to put pins on all modes not just engineer.
I'm thinking about running an external button to the tab key so site managers and collectors can access a few options like updating songs and volume control but if a cleaner or someone smart hits that button and goes into collector mode they can easily see how much money is it and decide whether to come back later and steal it or not.
If a punter is cheeky enough to find the button he'd definitely be tempted by a machine he knows has $500 in it waiting to be emptied.
However a simple pin code on each mode means only my collectors and managers can gain that information.