http://forum.unity3d.com/threads/76302-Pinch-Gesture-for-iOS-(v3.0)

Google before posting.

Thanks =).

I use the following code. It works but i guess there are better ways to do it.

float pinchLength = 0f;
void Update(){
  if(Input.touchCount == 2 && Input.GetTouch(1).phase == TouchPhase.Began){
    pinchLength = Vector2.Distance(Input.GetTouch(0).position, Input.GetTouch(1).position);
  }
  if(Input.touchCount == 2 && (Input.GetTouch(0).phase == TouchPhase.Moved || Input.GetTouch(1).phase == TouchPhase.Moved)){
    float deltaLength = Vector2.Distance(Input.GetTouch(0).position, Input.GetTouch(1).position);
    Game.cameraManager.ZoomBy(Mathf.Clamp(1f/pinchLength*(deltaLength),-1.5f,1.5f)); // ZoomBy(float Zoomfactor between -1.5x and +1.5x), eg orthographicSize
    pinchLength = Vector2.Distance(Input.GetTouch(0).position, Input.GetTouch(1).position);
  }
}

You might be interested in checking out the FingerGestures scripting package from the Asset store. This is pretty much what you're after. You can get more information in the forum thread at http://forum.unity3d.com/threads/95983-FingerGestures-Robust-input-gestures-at-your-fingertips!

There's a swipe utility in the Asset Store. I've not tried it myself yet, but it's nicely priced.