What is name of the fringe theme song?

JJ Abrams created the song. A simple search will find various interview videos where he explains the circumstances of the imagining and composing of the song. Sadly, it's a song that "just came to him", so it's probably only as long as the song on the episodes, unless he decides to embellish. That means, I would not hold my breath for it to be on iTunes any time soon except as maybe a show album after the first season.