Graphs Denote Threshold Breaches

I would love to be able to set a threshold on graphs on my dashboard so the graph itself shows there is some kind of issue. I watch this stuff all day and sometimes you don't notice obvious issues (especially on warnings where only mail is sent, not SMS). 

For example, I have a server and CPU goes critical. That could be a value from 0 - 100%. If it breaches 80% turn the background on the graph yellow, and maybe red at 90%. This would work equally well for any "fixed" number graph (memory, status of 1 or 0, thread count, etc.).

It would be a nice feature that might not be too hard to implement! It would sure point to potential issues quick, and give you time to deal with them before they go critical in some cases (where multiple samples are needed before it goes up the chain).

Thanks!
Dennis Stout