I use this tracker to help with tracking major tank CDs for M+ keys when you're healing. It'll track other CDs that might be useful like AMZ as well. Very useful if you have healer CDs and don't want to overlap CDs on the tank at the same time.
This is a modification of the Zentracker Front End Icons.
Note: It doesn't track Barkskin or Survival Instincts, mainly because if you have other druids other than your guardian druid, it'll track all of them and won't be able to help you differentiate between them. I don't have an answer for this unfortunately. :(