Electric saw detects fingers so it knows when to stop (youtube.com)

That's got to be some of the most unsafe workshop practices ever.

Never ever do it the way those guys in the video show, always use a push stick, and NEVER rely on a safety device to keep your ass safe, save it for the unavoidable.

The Sawdust Shop (http://sawdustshop.com/), near Fry's Sunnyvale, has one of these.

No one uses these because they destroy the machine, and they have too many false alarms. Especially a nail in the wood.

They need a device with zero cost for a false alarm.