I created an RFE for JON a while back that asked for stuff like "Process CPU time per minute", but it's not been implemented yet (AFAIK).
For GC data, at least in the AS7 plugin in RHQ/JON you have Server Configuration > platform-mbean > garbage-collector > Garbage Collector Resource where there's metrics for Collection Time and Collection Count per Minute which can be used to monitor GC activity. We use this for alerting on GC overhead.
I think for AS5+6 plugins the metrics were already there but I might remember wrong.
I found them. Thanks! There's such good support in this thing, pity it's going away... hawkular will be better I guess.
And yeah, Hawkular might be better, and with more features... in a couple of years time