A table saw that cuts wood but can't cut fingers

This is pretty impressive technology: http://www.sawstop.com/.  It detects the electrical characteristics of blood, and stops the sawblade in 3-5 milliseconds.  Making some reasonable assumptions, about 90% of that time is spent in detection, making the stop decision, moving the brake into position, etc.  Once the brake finally comes into contact with the sawblade at the end of that process, it takes roughly 500 microseconds to bring the sawteeth from 120mph down to zero, the equivalent of roughly 12,000G's.  The general contractor who showed me the saw says you hear a loud BANG!, the sawblade has vanished (the effects of angular momentum cause the blade to retract into the table faster than you can see), and all you have is a small nick on your finger that barely warrants a band-aid.  Replacing the blade and the brake will set you back about $100, but that is cheap compared to the alternative.  One flaw I noticed is the brake system requires power, so if there's a power failure, there's no finger protection until the sawblade comes to a stop.