Are you going to put a relay and switch on it? They will suck some juice so I wouldn't wire it with out a switch and a temp control switch. I wired one up with a temp swicth and an on off switch. Turn the switch on when the bottle is in the car and it will heat it to 90 degrees and turn off then if it cools it will turn back on. Then when you open the bottle you turn the switch off so it isn't sucking power going down the track.
I guess I have to figure out which heater I'm ging to get and than plan for wireing. If I'm going to use all of that stuff (which sounds like a good idea) than I should buy it first and than wire it up.
I have a dual voltage heater 120 volt and 12 volt and they work off a pressure switch attached to the bottle. I made a power box for the 120 volt and the 12 volt hook ups. I used a cigarette lighter plug and plug in for the 12 volt and used a relay inside each box to control power to the heaters. That way everything is externally wired and nothing but the 12 volt supply is inside the car. At the trailer I ues 120 volts and in staging you can use the car power or an outside 12 volt source to save your battery for racing. Just a thought.