Hi
There is not a custom metric that is build like the alerts. However you can build a custom metric for cpu wait or for a set of combined metrics. That is something you can do it the current version. Though this isn't it exactly, you can go into Options, Custom Metrics (under the 'Reports, Metrics, & Alerts) select the 'Create New Custom Metric' and add a sql statement in there similar to Custom Alert - CPU Utilization[1].
So, there isn't a built in way to do this like there is for alerts, but there still is a way to track it in the custom metrics section.
Kathy