How to check if you've stopped following.

[mmcookies]

Success! This is the extremely simple addon I wrote just now.
I run the 4 shammies on a second comp and monitor so this is perfect for me.
It makes the follow text big and bright yellow on my slave screens (with shadowed outline).
On breaking follow, it displays huge red text that fades away as normal.

function PM_BigFollow_OnLoad()
  this:RegisterEvent("AUTOFOLLOW_BEGIN");
  this:RegisterEvent("AUTOFOLLOW_END");
end;

function PM_BigFollow_OnEvent(event)
  if PM_IsSlave(UnitName("player")) then
    if event == "AUTOFOLLOW_BEGIN" then
      AutoFollowStatusText:SetFontObject(NumberFont_Outline_Huge);
      AutoFollowStatusText:SetTextHeight(40);
      AutoFollowStatusText:SetTextColor(1.0, 1.0, 0.0, 1.0);
    elseif event == "AUTOFOLLOW_END" then
      AutoFollowStatusText:SetFontObject(NumberFont_Outline_Huge);
      AutoFollowStatusText:SetTextHeight(80);
      AutoFollowStatusText:SetTextColor(1.0, 0.0, 0.0, 1.0);
    end;
  end;
end;