OP, you want to install a Webasto hydronic under hood heater with programmable and remote start.
They ain't cheap.
You probably should not even consider one unless you are planing to keep the vehicle for a very long time.
They burn a small amount of the fuel from the vehicles fuel tank, be it diesel, or gasoline. They make units for both, and in several sizes from cars and pick-ups to things as large as a bus. They have a glow plug that draws about 20 Amps for about a minute to initiate the combustion then a metal screen inside it that you can not see continually glows red hot to maintain the combustion. A solenoid type fuel pump that draws a small amount of electricity from the vehicles battery pumps fuel into the metal screen in the combustion chamber to maintain the fuel flow for combustion. A low power electric blower fan forces a small amount of fresh air into the combustion chamber. And an electric pump circulates the vehicles coolant through the heat exchanger that transfers heat from combustion chamber to the coolant. The entire unit is wired into the vehicles heating / cooling system and a microprocessor regulates the speed of the solenoid fuel pump, the combustion air fan, the coolant pump, and the vehicles heating / cooling system fan to blow heat into the cab of the vehicle, and varies the speeds of everything to initiate combustion, regulate rate of combustion and heat transfer with respect to demand,and shut down a heating cycle when combustion is no longer needed. On shut down the glow plus is energized for a short time to insure complete burn off of all fuel after the fuel pump is shut off. These systems also have safety temperature sensors and combustion sensors that are monitored by the microprocessor. They can be pre-programmed to start at a specific time, and can also be started remotely.
These systems do require regular maintenance to keep them running reliably. The metal screen that glows red hot in the combustion chamber eventually requires replacement because of left over carbon from combustion. You should probably replace that screen about the beginning of each winter. If you let it get too clogged it can be hard to remove from the combustion chamber. The glow plug probably should be replaced about every 5 years. The small solenoid fuel pump has a screen that should be cleaned or changed once in a while depending on the quality of the fuel. The electric motors that run the combustion air flow fan, and the coolant circulation pump, have brushes and eventually wear out and require replacement.
These units are nice, and quiet, and sip a very little amount of fuel, and draw a very small amount of electric power from the vehicles battery, and will warm the cab to the temperature selected on the units thermostat, that is usually added to the vehicles dash. They can put out an amazing amount of heat. You can have the inside of the cab toasty warm before you get it the vehicle, and all the ice melted off the windows. Along with heating the cab the hydronic units also pre-warm the engine by heating and circulating the coolant. This alone can make them worth installing in diesels in very cold climates because that makes the diesel engine easy to start.
They also make units that transfer the heat of combustion directly to air that is taken from the cab and blown back into the cab. However unless you have a large truck with plenty of room to mount one, you probably will loose a significant amount of trunk space by installing it in your trunk, and plumbing 4 inch diameter duct work to and from the cab.
Be it the under hood hydronic, or the air exchange units, they ain't cheap, and they do require maintenance, and their maintenance parts also cost money.
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Over all it can be cheaper and much less maintenance to just get a remote start and start the vehicle by remote in the morning about a half hour before you are going to leave the house.