I re-read your post and realized that I forgot to add any sort of check for your focus being a player, and a friendly one at that. This should do the trick.
Lua Code:
/run local n, r = UnitName("focus") if n and UnitIsPlayer("focus") and not UnitIsEnemy("player", "focus") then SendChatMessage("followme", "WHISPER", nil, n..(r and "-"..r or "")) end