I heard about an interesting tool today for vSphere that can collect diagnostic data about your vSphere environment then alert you about any potential problems to your vSphere environment before they can cause an outage.

The tool is called VMware vCenter Support Assistant and its a free download from VMware.
It works by regularly collecting support bundles (configuration and usage data) and transmitting them to VMware who will automatically match them to a list of known problems.

It is packaged as virtual appliance, the file is 648MB and it works with vCenter Server 5.1 / ESXi 5.0 or above

Available here:

https://my.vmware.com/web/vmware/details?downloadGroup=VCSA600&productId=491