How to half speed while s is down

var speed = 3.0;
var rotateSpeed = 3.0;
var BullitPrefab:Transform;
var jumpSpeed = 5.0;

function Update ()
{

       var controller : CharacterController = GetComponent(CharacterController);

       // Rotate around y = axis
       transform.Rotate(0, Input.GetAxis ("Horizontal") * rotateSpeed * Time.deltaTime, 0);

       // Move forward / backward
       var forward = transform.TransformDirection(Vector3.forward);
       var curSpeed = speed * Input.GetAxis ("Vertical");
       controller.SimpleMove(forward * curSpeed);

    if (Input.GetButtonDown("Jump"))
  {

        var bullit = Instantiate(BullitPrefab, 
        GameObject.Find("spawnpoint").transform.position, 
        Quaternion.identity);

    bullit.rigidbody.AddForce(transform.forward * 200);
var jumpSpeed = 5.0;

  }

RequireComponent(CharacterController);
}

here i have my player movement script how ever i want to half the speed of the player while the s key is down but when not pressed the speed is normal how would i go about this please help thanx ;)

Something like this should do it:

var curSpeed = speed * Input.GetAxis ("Vertical");
if (Input.GetKey(KeyCode.LeftShift)) {
    curSpeed *= 0.5;
}

(add the 'if statement' after your current vertical axis reading, and change the Key to whatever you want)

var realSpeed = speed;
if( Input.GetKey( KeyCode.S ) )
{
    realSpeed /= 2.0f;
}
var curSpeed = realSpeed * Input.GetAxis( "Vertical" );
// etc

easy version:

if(Input.GetKeyDown("s"))

{
speed = 1.5;
}

easy?? or not

var speed2 = speed;

if(Input.GetKeyDown("s")) { speed2 = 1.5; }

maybe this work i dont know

This is not really how it works. A Unity app on the iphone is basically the Unity virtual machine running your Unity game and it snags the whole window. You are much better off to reconstruct this interface using unity.

Just screen capture your interface, cut it up and make sprites/buttons. I have done this using cocos2d before, it works well.

Fighting with Cocoa Objects and Unity at the same time is more trouble than it is worth, seriously believe me man.