Head bolt heaters... I've never used or seen one but I have installed several block heaters that basically replace a freeze plug with the little heater element. It heats up the antifreeze and, being low on the engine, tended to keep the oil warm as well. Result was the antidepressants already warm so when you turn on the defrost, it work's now. On my truck, Ford put what amounts to a huge hair dryer element in the ductwork so even if I can't plug in my truck, it takes about 15 seconds to start blowing out warm air. Yeah, I'm belittle spoiled. If I remote start it when it is cold, it turns on the defrost, interior heat (and the instant heat element if it is colder out), mirror heaters, rear window defroster, steering wheel heat, and 4 seat heaters. The person in the middle back seat is out of luck. It does this if it is below 72. If it's above 72, it turns on the AC and the cooled front seats.
My Elio will probably sit in a garage but it will be outside all day while I'm at work and I'm sure I'll miss my truck every afternoon at least till my Elio warms up.