I removed the derived metrics from the cartridge to avoid performance issues.  You can find the rule in the cartridge. [URL]  OR...  You can download just the groovy script and run that from the script console/editor or set it up as a rule as well.  You just have to edit the custom attribute name you want it to make services for.  [URL]
I am currently running v6.7.1 which doesn't support the older cartridges.  What is the procedure to allow creation of a service for custom attributes that are setup in vCenter?  From blog post with the velocity cart method it looks like 6.7.1 should already be collecting the data.  How does one access that data to include in reports and create services from it?
VM Custom Attributes *without* the velocity cartridge