How skin to breathe? If you frozen just wear warm cloth LOL.

It's just a peltier, heatsink and watch strap. Why did they need 15 iterations of that?
It could also be made 50-75% smaller and still have the same effect. And be placed at a more strategic position, with more blood flow. Btw. I don't see a temperature sensor on any of the images. Hardware-wise this seems like a hobbyist afternoon project, it's only the fine tuning that might take some more time.

this would be awesome for endurance athletes! Its a billion dollar market. Racing in heat is always an issue for most and if they could keep their temperature down, it would be a HUGE advantage in terms of caloric savings! I hope this market gets explored.

It's a neat idea -- just from personal experience, running cold water over your wrist on a hot day makes you feel substantially cooler. But it appears that this is simply tricking the mind into making you feel cooler, rather than actually lowering body temperature...? I can see this could be a little dangerous. And considering the public resistance to just wearing warmer clothes, even with rapidly increasing energy costs, I struggle to see people rushing to strap heatsinks to themselves. That said, I'd probably still buy one, if just out of curiosity.

heavy sharp dangerous ugly would not cool or heat you anyway during exercise
i;d pay about $5 for it
how much is it, about $1000?
my wife won;t even put on a sweater she would be have to have a complete personality change to put this thing on..
wle

All the same, I want one!

Want to be cool and look weird at the same time? Take a couple of old CPU heatsinks with fans and fashion something to hold them to either side of your neck, over the carotid arteries and jugular veins.
Connect a 9V battery to the fans and you'll feel like you've strapped a couple small blocks of ice to your neck.

I already have an item that can make me feel warmer without increasing energy consumption. It's called a sweater.
As for cooling, the Sharper Image and other gadget stores have sold powered evaporative personal cooling collars for many years. Much less likely to be damaged than a wrist-mounted device. Or make an unpowered version using sodium polyacrylate or something similar as a gel inside a fabric cover.

I would love this and all menopausal women will thank you!

I worked with peltier thermoelectrics for about ten years, and one thing which is still true to this day is inefficient of energy these devices are!...The technology has along way to go before they can be used effectively and cost$ to purpose of it's use in any manner worthy of.