The technology behind exo2 heated clothes is FabRoc™

Battery Heated Socks - webBikeWorld
Turtle Fur - Lectra Sox Battery Heated Socks
To evaluate the heat difference that these socks might offer, I inserted a battery on one battery heated sock on my right foot and I put the other sock on my left foot, but without a battery.
Unfortunately, as hard as I tried, I could not tell one bit of difference between the sock with the battery and the sock without. I then switched the battery over to the other sock -- same result.

Heated Socks | ** Heated Socks Guides And Reviews **

Battery Heated Sock Liners - - ActiVHeat®
Gerbing's Heated Clothing / The World's Warmest Clothing! Cabela's Battery Heated Wader Socks, Men's Hunting Socks, Men's Socks, Men's Footwear, Footwear : Cabela's

last updated 19 Oct 2011