Is there a way to only trigger the dbm sensor alert if the corresponding interface is up? I thought I could get away with just testing if the sensor values fall outside the sensor limits. But when ports are down (even when unplugged) I get spiky readings which will trigger the alert. So it would be nice to check if the interface is up as part of the alert check. 

I suspect this isn't possible as things are right now. It seems sensors have no relationship to another entity (e.g a port on a router). Ideally, I would like to say something like this:

Port Checker Condition

Port Checker Entity Match

So only ports that are admin up and have an associated sensor type of the appropriate type would get added to the checker. This will ensure the condition will be able to refer to the appropriate sensor. 

This would imply there is some mapping/relationship between sensors and other entities. This is probably very MIB specific and very platform specific. But it would make for a very useful checker.