[Observium] traffic alert to a tunnel interface?

Hello

I have some GRE tunnels without physical interface speed and theye are always in UP state. So in this case i am not able to set an alert to notify me when "ifInOctets perc le 1" or if the interface status is down.

Is there any options to set up a byte/sec alert ex: i would like to get an alert if the average traffic is lower than 100 byte/sec in the last 5 mins ?

Thanks

Laszlo