Cops need dead-man signals

I believe that technology is ready to allow police and other folks to have something on their body that monitors their vital signs and constantly transmits an OK signal to a robot with a phone. Every time a cop is shot a signal would go off somewhere and a battalion of SWAT would swarm down on the area. Something similar could happen with bank tellers or liquor store clerks. Heck, why not use it for heart patients.

I figure an algorithm could be constructed that could identify the state of well beeping. That is, you could tell by the body's reaction if someone has a gun to their head. There would be false alarms of course. it would take a while to work out the kinks.