So, I bought Just Dance 2016 just now! and I wondering if I should buy PS4 Camera along with it

I have a few questions and I would really appreciate if someone can answer those questions

How accurate is the Controller app itself compared to Motion tracking camera?
The controller apps only measure 1 hand right? How Ubisoft track other body parts (e.g. the other hand) being moved?

How about the Camera? Does it track all top-half of the body?

Thanks!