Notify if Interface Activity falls below threshold after a few minutes (not seconds like traffic monitor)

Scenario. I have a VOIP device that will all of a sudden stop transmitting UDP packets. Only does this maybe 2 times a month. However, I can still ping it and send it commands. I have netwatch configured but again, I can always ping it. I would like some ideas on how to monitor it when traffic stop flowing. Ive tried the /tools traffic monitor but it checks to frequent. I am trying to figure out how I could detect if the interface has falling below say 50kb of traffic in last few minutes.
Thanks!