I'm trying to build a kill switch in my car so that when I turn the ignition, a button also has to be held down. When the power goes through, the button can be let go and the system stays closed until the car shuts down, then you have to repeat the process. I came up with this diagram:
What kind of parts does it take to build this? I drew logic gates but I have no idea how that translates to real components. Is a button and relay from an electronics store enough? I'm worried about 1) splitting the ignition wire like that and 2) how much power actually loops back, would things over heat?