The Vita is for Remote Play only
Rayman Legends is a pretty great platformer, and it's coming to the Xbox One and PS4 this week. To help alleviate some of the questions fans have about the PS4 game specifically, Sony has provided a fan Q&A piece on the PlayStation Blog.
Arguably the biggest question is from a fan in the Netherlands, who asks whether or not the Vita can be used like the GamePad was on the Wii U. The short answer is "no" - it can only used for Remote Play purposes.
Well, it would have been neat to control Murfy, but it's not really an essential part of the game anyways.
Rayman Legends on PS4: Your Questions Answered [PlayStation Blog]