Yes, the device is also a car alarm that is triggered by internal lights that come on when the vehicle door is opened.
The line is 12 Volts live until a door is opened & a resistor divider provides 5 Volts for the pic's input.
If ever I get a false alarm, I want to save the last thirty seconds voltage readings to see if I can prevent it.

When the car battery goes cactus my alarm might also sound since the resistor divider is at the unregulated side,
and may not produce the voltage for logic high at the pic pin.

I could have the program look at the last thirty seconds values to prevent these false triggers.