Sawstop

[John]

Apologies if this has been discussed here before but I've only just seen this and it's bloody amazing!! A table saw that stops if it hits your finger

[Huge]

Many times.

. but I've only just seen

I wonder what the rate of false positives is?

[John Rumm]

know how well it works with accidents like a hand hitting to top of the blade, or if there are things that can trigger it by mistake (say damp wood etc).

IIRC the cost of replacement bits required each time it triggers is also pretty high - so I would want to be sure its not going to go by mistake! The saws themselves are also two to three times the price of a equivalent "ordinary" saw.