SIGAR is a cross-platform API for system-level metrics. SIGAR allows Hyperic HQ, Hyperic's flagship software, to grab system metrics from a variety of platforms. SIGAR is written in Java and C.
A new release of Hyperic SIGAR is available now - SIGAR 1.3. In this release, new support has been added for VMware.
For all of the info on SIGAR: