Reverse cycle air con for the car

[mik]

Just talking to my brother the other day , dunno how it come up but apparently some of these electric cars have reverse cycle heating/air conditioning, for reasons .....ala no internal combustion engine with a cooling system to bypass hot water to a heater core.
my brother seems to think with a bit of plumbing and valving it wouldn't be too hard to do.
now when my brother says things like this we must be wary......hes a bit different, he gets an idea in head and most others would say get outa town (me included), but he usually does what he says......eventually.
Now if a bloke was looking at dash out job i`m thinking this might be an alternative as all the work would (i think ???) need to be done in the engine bay.
so do we have any one been down this path or do we have any aircon guys that can comment on this to say yay it could be a worthwhile thing or forget it.