When trying to diagnose a problem I often try to compare several sensors. For example, several ping graphs, a jitter and traffic sensor etc.
If there was some method to drag several sensors onto a "compare" button or something similar.
Also, on a separate note. Rather than defined 2 day/30 day graphs, can you implement a slider so that you can have better control over what size you want the graph. Often I would like a week or something similar which can't really be seen on the 30 day.