HASS has the ability to send you alerts when a device/sensor is considered to be offline (so you could definite it as it’s offline if it hasn’t sent you an update in 28 hours or some such). You can also set it up to send you regular notifications too. Or you could just have this data in the dashboard and check it once in a while. Nothing really prevents you from doing all this but also utilizing a tool like that to WUPHF.com you soon as there is an issue.