There's a new version (20160531) of the Monitoring Plugin to monitor the hardware of ESXi servers, check_esxi_hardware.py, out! This version contains a new feature which allows manually define the CIM port.
The default CIM port listens on tcp/5989. However if you have several ESXi servers behind one IP address (NAT) you can now use port forwardings on your firewall our router and monitor all of them, too.
The newly added parameter is "-C" (--cimport). Documentation of check_esxi_hardware is up to date, too.