А взять любую триггерную кнопку типа п2к и кинуть 12 вольт через нее на Vcc это некошерно?
Или я что-то упустил важное в работе предлагаемой схемы?
Damn it. The chinese could have solved it so easely with software that grabs a config file where the user can choose the amount of time the unit stay on (1, 10,15 20, 30mins...) with a disabled backlight after ACC off. But the 1min time is hardcoded in the library.

They changed it from 0 min (c20140413) to 1min (c20140419). It is purely software, the MCU just give the sign that ACC is off.
I asked already through email, but did not get any response at all from SNTRON.
To make it through hardware, one could create a timer with 2 Relay. When ACC is off the relay 1(connected to the power button of the unit) activates to disable the backlight/sound aso. The second relay gets disabled after a configured time lets say 15min. After the 15mins, relay 2 gets off and the unit clearly see an ACC off and shuts down after 1min.