Actually this reminds me of this show I saw on a new invention which allowed a person to sit in a chair on a REALLY hot day and cool themself off by putting their wrists into pockets of watery ice. The theory was that when you are overheating, people tend to think putting ice on the top of their head will cool them down. Not so...if you are overheating, you are heating from the inside so what this dude suggested doing is putting the ice/water next to a main artery and cool yourself that way. I forget most of the justification behind it but it seemed to make sense to me. If you can cool your core temp. you will be cooler.
I thought it was interesting.

Bump.

my 2 pennies:

The concept is sound - a light colored, hydophobic, thin material on you arms should spread your sweat evenly to achieve a swamp cooler effect. This is much better than your sweat dripping onto the black top as you ride by. As you get hot, your body dumps blood to the surface area (skin) to try and cool itself by the evaporative effects of sweating. These things should also keep the direct sun off more of your body (meaning, in addition to your tri get-up).

If you live in a high humidity area... less effect, duh. Oh ya, they don't work in Kansas, California, or LA (lower Alabama) - so don't try 'em, y'all.

This is the same concept that has been utilized for generation in hot/dry parts of the world - Middle East, for example.