Hi
Perhaps this can help: https://kb.op5.com/display/HOWTOs/Monitoring+VMware+ESX+3.x,+ESXi,+vSphere+4+and+vCenter+Server
And this is an overview of the commands / subcommands: https://kb.op5.com/pages/viewpage.action?pageId=3801484
And here is the plugin: http://www.op5.org/community/plugin-inventory/op5-projects/check-esx-plugin
Hope it can help // Jan