That's got to be some of the most unsafe workshop practices ever.<p>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.
No one uses these because they destroy the machine, and they have too many false alarms. Especially a nail in the wood.<p>They need a device with zero cost for a false alarm.