Some systems already have that. Replaced a switch yesterday and re-arranged some things on my network board and got a HomeKit notification that some things were offline and when it came back. Knowing when something goes offline isn’t as useful as keeping things up though. With something like a hardwired camera/NVR, even if your ISP service is interrupted the cameras can still record, and you can put a UPS there to keep things going, even if the rest of the network is down.