Any advice on how can we monitor the vRNI and vRLI appliances itself.
For vRLI I think that the documentation states that you need another log insight server for that. But maybe someone else has actual experience with this?
One of the way I can think of is monitor the appliance up/down status using vROPS. Is there any other bettery way to achieve this monitoring?
It depends on your version and setup. And off course what you want to monitor.
With vROPs 8.1 you can configure both as endpoints. And if any one of the apps fails to send data back you'll get an alert. Is that enough?