does php ring a bell?

(Please excuse if this is dupe.. Think the first went to a wrong list.) I am thinking it would be nice to have chat running on our club's pages... But, when someone comes to talk, will anyone else be there? Is it possible for them to call me and/or other members to the chat page from the chat site? I am thinking of something like a form button that would check for member(s) who on line and on finding any, call them? (Perhaps the same as AIM and other chats use?) Not sure how those others work but it seems if I sent my dns to a database or flat file, when I was on line, it could be picked up by an action page, on a click from the club site, and used to call me? I would like it to ring a bell or something. A .wav or pop up window, at my end... Is it being done? Any thoughts? Many thanks.. Floyd --