Does anyone know of a way I can monitor sensors available. For instance get alerts if a sensor has been unavailable for a period of time?
Simple Device Viewer will do this for you!
Also, have you enabled Device Health: with this you will be able to see devices that are offline or in a low battery state.
As an example, here’s what Device Health will show if a device stops responding. I may not have mine set right, but it took about 3 days before it showed me that this mutli-purpose sensor was offline. And i didn’t receive a notification - I just happened to see the the red triangle on the device. Simple Device Viewer - which I linked above - will let you set push/text notifications at a custom interval if a device stops responding.
This only works with devices that support the Health Check capability and some of the built-in device handlers and most of the community created device handlers don’t.
That capability hasn’t been documented yet so it will probably be a while before most of the community created device handlers support it.