While it doesn't justify the purchase of a new model just to get it, this "R.P.M. Blender" from L'Equip has a tachometer on the side. It does seem sort of obvious now that someone's made one, doesn't it? I'd like to see this added to all blenders as standard issue.
The R.P.M. is powered by a 900 watt motor that can spin up to 20,000 revolutions per minute. It's available for $134 plus shipping.