Mod Exist? [[shows active member when a new post is made in subscribed thread]]

[JacquiiDesigns]

I'm looking for a modification for the vBulletin 3.x series. The modification is a installable product that notifies an active member when a new post has been made in one of his/her subscribed threads... Or even a modification that will show when a new post is made in a thread that an active member has just posted in. Like when 2 members post simultaneously - the modification will pop-up a message letting the member know that there's a new post in that thread.

Does this modification even exist? If yes - can someone please link to it.
Thanks in advance

Jacquii.