How rotate the cam by acceleration

Hallo, i am new with Unity3d. I want create an Iphone app. I have i scene with a car and in the middle of the car is a cam. I want to rotate the cam at 360 degrees, so that i can see the hole inside of the car. I tried it by using acceleration, but the problem is the rotation don't stop. I want to rotate the camera in the scene in the direction in which I hold the iphone. I don't want a permanent rotation. The code the i tried is the follow:

// Move object using accelerometer var speed = 10.0;

function Update () { var dir : Vector3 = Vector3.zero;

 // we assume that device is held parallel to the ground
   
 dir.y = -Input.acceleration.y;
 dir.x = Input.acceleration.x;
  
 
 // clamp acceleration vector to unit sphere
 if (dir.sqrMagnitude > 1)
     dir.Normalize();
 
 // Make it move 10 meters per second instead of 10 meters per frame...
 dir *= Time.deltaTime;
     
 // Move object
 transform.Rotate(dir * speed);

}

I think it must stop after the first rotation. i hope someone can help me.