[Kanegasi]

Trigger:

function() return IsResting() end

Untrigger:

function() return not IsResting() end

Edit: I don't know if WeakAuras supports direct textures, but this is the data for the rest icon:

Texture: Interface\CharacterFrame\UI-StateIcon
Texcoords: 0, 0.5, 0, 0.421875

There's also an icon with "ZZZ", but it has a "x2" on it. WeakAuras has an icon box for this: 648642

This is what the icon looks like: https://www.wowhead.com/icon=648642