Very clever idea. The only downside is its alot of work to convert a chunk of wood into a beer koozie like this. I wonder if I could simplify it with a square block instead? The “blanks” the author uses are $10 and up (not including shipping). And the bottle opener is clever, but is $6 at Rockler (called an Inset Bottle Opener). So the problem looks cool, but is pricey.
http://www.instructables.com/id/Wooden-Beer-Koozie-W-Built-in-Bottle-Opener/?ALLSTEPS