Hi @alferna,
Thanks for your patience so far!
To answer your question, I don't think Webex would have the compatibility to be used on a third-party App and I'm not even sure if Nagios would have the option to be integrated with the Webex APIs.
Definitely, you can build an independent monitoring system using the Webex Calling APIs to fulfil certain requirements, but building it with the Nagios won't be possible.
Hope that helps!
Please let us know for any further assistance on the same.
Regards!
Sandip