Currently you can set threshold alerts for various monitors, where the threshold is an absolute value.
However, not all graphs go down - some only go up (buffer hits for a router, for example). In these instances, an absolute threshold value isn't much use; what would be nice is a "rate of change" threshold.
By looking at the graph, you can see what a "normal" rate of change might be. On one of my routers, the "Medium Buffer Hits" counter goes up by about 15,000 per hour on average. I'd like to be able to say:
"Alert me if the Medium Buffer Hits counter increases by more than 30,000 in one hour"
It's a kind of baseline monitoring - 15,000 per hour is normal, 30,000 per hour is not.