I know that people have made macros to alert you when certain pets are nearby. You might have to spam it when you're in the area you're farming, but they work.
Here's the one I used when I was farming Unborn Val'kyr; I found it in a Wowhead comment (Thank you, Shaw!) on the Unborn Val'kyr page:
/tar Unborn Val'kyr
/run RaidNotice_AddMessage(RaidBossEmoteFrame,"Unborn Val'kyr!", ChatTypeInfo["RAID_WARNING"])