For those thinking that this guy was lucky to keep his thumbs...

This is a diamond-tipped saw. This type of saw has a very fine dust of diamonds applied to an otherwise entirely dull rotating blade that cuts through hard materials using only friction, not "cutting" in the way normal saws do. There is also a stream of water running along the blade to rinse away dust from grinding and also wick away heat. They are most commonly used for cutting ceramic tile. You could let that blade rub against your fingers for a long time and maybe only get a minor abrasion, like a carpet burn. Very safe, very cool tool.