We've historically avoided offering support for metrics collection in Beaker, on the assumption that adding it would be difficult.
After discussion with Nathan Scott at PyCon AU, it looks like it may be easier than we feared to add at least a basic metrics collection capability.
As a starting point, Nathan suggested using "pmlogger"  to collect the logs remotely from the lab controller. This could be handled by the watchdog daemon, similar to the console logs.
This would be opt-in, both to avoid wasting space on the log when the metrics aren't needed, as well as to ensure we don't interfere with PCP's own testing.