Kevin Hilscher just wrote “check_vmfs”, a Perl plug-in for Nagios.
Similar to the check_disk plug-in, check_vmfs monitors the free space available on vmfs volumes and will return warning or critical messages to nagios based on user-defined thresholds (ie: warn at 10%, critical at 5%). The check_vmfs plug-in must be executed remotely using the check_by_ssh plug-in because check_vmfs uses the VMware “vdf” command behind the scenes, and the vdf command must be executed as a root user.
You can download it here.