This addon registers incoming whisper events.

DoMe = LibStub("AceAddon-3.0"):NewAddon("DoMe", "AceConsole-3.0", "AceEvent-3.0")

function DoMe:OnInitialize()
    self:Print("OnInitialize")
end

DoMe:RegisterChatCommand("dm", "Slash")

function DoMe:Slash(input)
    if (input == "?" or input == "") then
        self:Print("This addon registers incoming whisper events.")
        self:Print("Current events:")
        self:Print("followme - You follow the player who's sending whisper.")
        self:Print("leaveparty - If member of a party and you recieve this whisper, you leave the party.")
        self:Print("In order for this addon to work on both sides, it requires that both players have it.")
    end
end

function DoMe:OnEnable()
    self:RegisterEvent("CHAT_MSG_WHISPER")
end

function DoMe:CHAT_MSG_WHISPER(arg1,w,name,arg4,arg5,guid)
    if (w == "followme") then
        FollowUnit(guid)
        self:Print("Following "..name..".")
    end
    if (w == "leaveparty") then
        LeaveParty()
        self:Print("Leaving party. Requested by "..name..".")
    end
end