I suppose it’s a high tech version of the neckerchief I bought in Australia; it contained crystals, which when soaked well in water, expanded. Tied round my neck it kept me fairly cool due to evaporation - and those temperatures were far too hot for me!
The drawback was the thickish roll of crystals round my neck, which was a little restrictive, although not nearly as restrictive as the Blaux must be and much cheaper and easier to pack. I think I still have my neckerchief in a drawer somewhere.