Doing some research it looks like you can use the NDOUtils plugin to export your monitoring data from Nagios to a MySQL database that you should be able to connect to with Tableau. More info on the plugin can be found here: NDOUtils - Nagios Exchange
I would imagine that you could also try connecting directly to a copy of the .csv file that the monitoring data is stored in: Where Does Nagios Save Data For The Service It Monitors?? - View topic • Support Forum • Nagios
Wish I knew more about Nagios and could offer some more help!
Thanks, Patrick. I'll definitely check that out.