Long-haul freight trains and other systems that required an alert operator for safety would often implement a "dead-man" switch that would shut the system down if the operator couldn't actuate the switch in a timely fashion. Some time ago the military spent money on IFF (Identify Friend-or-Foe) systems to reduce friendly fire incidents. Wood workers sick of losing fingers to table saws got a clever SawStop system a few years ago: a circuit that drops the blade below the table if it senses the capacitance of a human body.
I began wondering why electricians don't have safety systems like that: that clamp and/or divert current away from a worker, or at least his heart. We do have GFCI breakers that can protect us from grounding a hot supply. But when we sit down to work on high voltage gear could we construct a circuit that breaks a power supply if it senses current across our chest? (The trick would be to avoid creating a circuit: i.e., do something better than just connecting a conductive patch over your heart to the neutral/ground and relying on GFCI/AFCI breakers, because then you'd trip the supply during contacts that, absent that excellent ground, wouldn't produce a dangerous shock.)
(This is mostly a "thought exercise" question, because I realize such a system wouldn't mitigate all electrical hazards. I guess if we wanted to avoid getting killed by all electrical risks, including things like discharging capacitors, we could wear a conductive shirt, so in the worst case we'd only get burned from points of contact up to the first good contact with the shirt?)