If a Nintex Gateway goes offline, currently the only way to check that I'm aware of is to either go into the NAC settings section, check the Nintex Gateway and see that it's not "Online" or go to the Gateway Server itself and open up the console for the Gateway and see that the "Retry" option is available.
Currently, I can't monitor the service, because, connected or not, it is running, just with a disconnected status internally. Since the service is running, SCOM/Splunk/Etc. sees it as "Ok"
It would be really nice if there was a way to alert the admins before the user community starts complaining that things aren't working. I know that we could do an hourly manual check, but that's not what I expect out of an enterprise level application.
Something similar to https://status.nintex.com/ that are customer specific, that could query connector status and alert through a subscription model, could solve this. And clear connector availability, at the App Layer, could be fed into other reporting/operations services, like SCOM or Splunk.