Hi Gary,
The healthStatus is not a standard HE attribute as per today, but it already used by a number of custom drivers and popular apps/integrations like the Device Activity Check, HubiThings Replica, Home Asistant Device Bridge. It is a good way to determine whether a device is online or offline to the HE hub, based on device-specific behavior.
It will be great if the healthStatus is added in the Attribute Monitor list.
