Hmmm, interesting notion. What I have visualized in my head is a helmet that has 2 small fittings attached that will circulate chilled water through a lined compartment in the shell. The water would be carried in and out via 2 hoses to what amounts to an external "cold box". Kind of reminds me of a similar setup that I have seen drivers in NASCAR and possibly other forms of motor sports use. This proposed system uses water as opposed to chilled air. I guess the only concern(s) there in my mind would be do you feel comfortable being tethered to something. And where do you mount the external unit. Also, would the rider be able to hear the water circulating through the shell. That would be interesting! I also wonder how much extra weight would be added to the helmet. Wouldn't seem like much.
I myself am not sure if I would feel comfortable with that. The same thing goes for electrical gear for cold weather applications. But that is just me. I'm sure most would not mind at all if the obvious benefit was there. For extreme environments This could be great. All in all a pretty interesting idea...
Play Hard, Ride Safe