How do I electrically kill the engine and know if it's in park?

I'd like to build a security device for my truck to help keep it from being stolen when it is idling.

The device would work off of a hidden switch, just like a kill switch. When the truck is on, you could flip the switch which will enable the device. When the truck is pulled out of park, this will kill the engine and latch the engine it off. Once it is latched, you wouldn't be able to start the truck until you push a button securely hidden under the hood.

I have all the logic worked out, but there are two parts that I need to know.

First, how do I know if the truck is in park? Obviously there is a needle, but does this ever turn into an electrical signal somewhere?

If there isn't, does anyone have any ideas how you could hook up a switch or something that would be reliable?

I could use the break as a last resort, but you don't really need the break to drive. Especially if you are in a hurry. :)

The second thing I need to know is, how do I electrically kill the engine? In a gasser, this couldn't be simpler, but I am unfamiliar with these old diesels and I can't think of anything.

Thanks!