I think the 'gaping hole in the dash' is a far better theft deterrent than anything you could do with detachable face plates, hardware locks, or software codes. Especially since the unit is pretty much designed to be pulled out of its sled and the new front panel will make it look more like a car audio component and less like an anonymous piece of fascia.

Otherwise, try using the roof light.

Save the whales. Feed the hungry. Free the mallocs.