sourceSony Computer Entertainment President of Worldwide Studios Shuhei Yoshida has confirmed the PlayStation Vita can only be used as a PlayStation 4 controller for games "specifically programmed" to utilize it.
The clarification came via Yoshida's Twitter account, when a user asked if PlayStation 4's portable buddy could be used as a secondary controller. "In a normal sense, no," responded Yoshida. "Unless a game is specifically programmed to allow such use of PS Vita."
I don't see why it wouldn't work for everything.