If there is a defined priest in your dungeon group, he will be written "PI ME NOW DUDE!!!" as soon as a defined spell is executed.
Enter the following in the custom options:
Spell ID's = [The ID's of the spell you want to whisper at the priest].
Priest Names = [The names of the priests that have to be in the group for the Weakaura to take effect].
Whisper Text = [The text to be whispered to the priest].