Ultimately, what good will a device telling you your partner is already dead do?
I can understand proactive measures to get help but a pulse of 0 is going to be far too late.
Take a heart attack as an example, heart rate will seemingly randomly either increase or decrease or it might even stay the same with an abnormal rhythm, etc. These rhythms are detectable, for example, with an apple watch.
I can understand the mental reassurance that your partner is "okay" by seeing a heart beat exist but this may be a false sense of security if they need help while still alive?