Do you mean, when you click a stone to summon someone, it prints in part/raid:
Now summoning: <Name> to <instance name>?
Or Sends the user you're summoning a whisper?
I know of an addon that does this for locks and their summoning portal. I believe it was called.... Necrosis
But I believe it was only for warlocks.
It adds macros for summons, and portals. EG: /say I summon you to my side <pet name> or something similar.
No, it's not for the person that initiates the port but for myself when somebody wants to port me. I've found an addon that does this (and a lot more). Automaton. It's not developed anymore (as far as I know) but it still works with 3.2.
What I don't get is that you want an addon to notify you. Doesn't the base UI pop up a message saying who wants to port you to where, with an OK and Cancel? Lasts 2 minutes and all that?
I hooked that action for the battleground "enter or hide?" popups to also print a line in the main chat window. Reason is that I play windowed+maximized, and often alt-tab out to browse or code. So there's usually stuff sitting over the screen space where the popups appear, but the lower left corner of the WoW client is still visible.
local f = StaticPopupDialogs["CONFIRM_BATTLEFIELD_ENTRY"].OnShow
StaticPopupDialogs["CONFIRM_BATTLEFIELD_ENTRY"].OnShow = function(data)
addon:Print("Battleground is ready!")
if f then f(data) end