how to use gui buttons as input get axis for mobile?

I tried some ways to do it, but they didn't worked. Here is my scripts (based on the tutorial series car controller kit, by flat tutorial), I started converting them to use in mobile, and I already got to set up the acelerometer, but the touch inputs are still missing.

WheelScript:

 enum wheelType { Steer , SteerAndMotor , Motor , JustAWheel}; 
 var typeOfWheel : wheelType;    
 var handBreakable : boolean = false;    
 var invertSteer : boolean = false;    
 var wheelTransform : Transform;        
 var zeroAc: Vector3;
 var curAc: Vector3;
 var sensH: float = 10;
 var sensV: float = 10;
 var smooth: float = 0.5;
 var GetAxisH: float = 0;
 var GetAxisV: float = 0;
 private var speedFactor : float;    
 private var wheelCollider : WheelCollider;        
 private var carScript : CarControleScript;        
 private var mySidewayFriction : float;    
 private var myForwardFriction : float;    
 private var slipSidewayFriction : float;    
 private var slipForwardFriction : float;    
 private var axisH: float = 0;
 private var axisV: float = 0;
 
 function ResetAxes(){
     zeroAc = Input.acceleration;
     curAc = Vector3.zero;
     }
 
 function Start () {
 wheelCollider = gameObject.GetComponent(WheelCollider);
 carScript = transform.root.gameObject.GetComponent("CarControleScript");
 SetValues();
 ResetAxes();
 }
 
 
 function SetValues(){
 
 myForwardFriction  = wheelCollider.forwardFriction.stiffness;
 mySidewayFriction  = wheelCollider.sidewaysFriction.stiffness;
 slipForwardFriction = 0.05;
 slipSidewayFriction = 0.085;
 
 }
 
 
 function Update () {
 WheelPosition();
 ReverseSlip();
 
 wheelTransform.Rotate(wheelCollider.rpm/60*360*Time.deltaTime,0,0);
 if (typeOfWheel == wheelType.Steer || typeOfWheel == wheelType.SteerAndMotor)
 wheelTransform.localEulerAngles.y = wheelCollider.steerAngle - wheelTransform.localEulerAngles.z;
     
 curAc = Vector3.Lerp(curAc, Input.acceleration-zeroAc, Time.deltaTime/smooth);
     GetAxisV = Mathf.Clamp(curAc.y * sensV, -1, 1);
     GetAxisH = Mathf.Clamp(curAc.x * sensH, -1, 1);
 }
 
 
 
 function FixedUpdate (){
 if (typeOfWheel == wheelType.Motor || typeOfWheel == wheelType.SteerAndMotor){
 TorqueControle ();
 }
 if (typeOfWheel == wheelType.Steer || typeOfWheel == wheelType.SteerAndMotor){
 SteerControle ();
 }
 if (handBreakable){
 HandBrake();
 }
 if(!carScript.braked){
 Decellaration();
 }
 }
 
 function InputGetAxis(axis: String): float {
      var v = Input.GetAxis(axis);
     if (Mathf.Abs(v) > 0.005) return v;
     if (axis=="Horizontal") return axisH;
     if (axis=="Vertical") return axisV;
 }
 function OnGUI() {
 
     axisV = axisH = 0;
     if (GUI.RepeatButton( Rect( 10, 435, 100, 35 ), "Forward" ) ) axisV = 1;
     if (GUI.RepeatButton( Rect( 690, 435, 100, 35 ), "Backward" ) ) axisV = -1;
 }
 
 
 function WheelPosition(){
 var hit : RaycastHit;
 var wheelPos : Vector3;
 
 if (Physics.Raycast(transform.position, -transform.up,hit,wheelCollider.radius+wheelCollider.suspensionDistance) ){
 wheelPos = hit.point+transform.up * wheelCollider.radius;
 }
 else {
 wheelPos = transform.position -transform.up* wheelCollider.suspensionDistance; 
 }
 wheelTransform.position = wheelPos;
 }
 
 
 
 
 function Decellaration(){
 if (Input.GetButton("Vertical")==false){
 wheelCollider.brakeTorque = carScript.decellarationSpeed;
 }
 else{
 wheelCollider.brakeTorque = 0;
 }
 }
 
 
 
 function SteerControle (){
 speedFactor = transform.parent.root.rigidbody.velocity.magnitude/carScript.lowestSteerAtSpeed;
 var currentSteerAngel = Mathf.Lerp(carScript.lowSpeedSteerAngel,carScript.highSpeedSteerAngel,speedFactor);
 if (invertSteer)
 currentSteerAngel *= -GetAxisH;
 else 
 currentSteerAngel *= GetAxisH;
 wheelCollider.steerAngle = currentSteerAngel;
 }
 
 
 
 
 function TorqueControle (){
 if (carScript.currentSpeed < carScript.topSpeed && carScript.currentSpeed > -carScript.maxReverseSpeed && !carScript.braked){
 wheelCollider.motorTorque = carScript.maxTorque * Input.GetAxis( "Vertical" );
 }
 else {
 wheelCollider.motorTorque =0;
 }
 }
 
 
 function HandBrake(){
 if (carScript.braked){
 if (carScript.currentSpeed > 1){
 SetRearSlip(slipForwardFriction ,slipSidewayFriction); 
 }
 else if (carScript.currentSpeed < 0){
 SetRearSlip(1 ,1); 
 }
 wheelCollider.brakeTorque = carScript.maxBrakeTorque;
 wheelCollider.motorTorque =0;
 if (carScript.currentSpeed < 1 && carScript.currentSpeed > -1){
 carScript.backLightObject.renderer.material = carScript.idleLightMaterial;
 }
 else {
 carScript.backLightObject.renderer.material = carScript.brakeLightMaterial;
 }
 }
 else {
 wheelCollider.brakeTorque = 0;
 SetRearSlip(myForwardFriction ,mySidewayFriction); 
 }
 }
 
 
 function ReverseSlip(){
 if (carScript.currentSpeed <0){
 SetFrontSlip(slipForwardFriction ,slipSidewayFriction); 
 }
 else {
 SetFrontSlip(myForwardFriction ,mySidewayFriction);
 }
 }
 
 
 function SetRearSlip (currentForwardFriction : float,currentSidewayFriction : float){
 if (typeOfWheel == wheelType.Motor || typeOfWheel == wheelType.SteerAndMotor && !carScript.braked){
 wheelCollider.forwardFriction.stiffness = currentForwardFriction;
 wheelCollider.sidewaysFriction.stiffness = currentSidewayFriction;
 }
 }
 function SetFrontSlip (currentForwardFriction : float,currentSidewayFriction : float){
 if (typeOfWheel == wheelType.Steer || typeOfWheel == wheelType.SteerAndMotor && !carScript.braked){
 wheelCollider.forwardFriction.stiffness = currentForwardFriction;
 wheelCollider.sidewaysFriction.stiffness = currentSidewayFriction;
 }
 }

Car controle script:

 var centerOfMass : Vector3;    //Center of mass
     var dataWheel : WheelCollider;    //Wheel Collider from which you want to calculate the speed
     var lowestSteerAtSpeed : float = 50;    //if lowestSteerAtSpeed < currentSpeed the steer Angle = highSpeedSteerAngel
     var lowSpeedSteerAngel : float = 10;    //This could be a high value
     var highSpeedSteerAngel : float = 1;    //This shouldn't be a high value (recomended for stability of car)
     var decellarationSpeed : float = 30;    //How fast the car will decellarate
     var maxTorque : float  = 50;    //Maximum Torque
     var currentSpeed : float;        //Current Speed of car
     var topSpeed : float = 150;        //Highest speed at which the car can go
     var maxReverseSpeed : float = 50;     //Highest Reverse speed
     var backLightObject : GameObject;    //Mesh for reverse light
     var idleLightMaterial : Material;    //for idle state
     var brakeLightMaterial : Material;     //Braked state
     var reverseLightMaterial : Material;    //Reverse state
     @HideInInspector    
     var braked : boolean = false;    //Brake trigger
     var maxBrakeTorque : float = 100;     //Braking speed
     var speedOMeterDial : Texture2D;    //GUI Texture for dial
     var speedOMeterPointer : Texture2D;        //GUI Texture for needle
     var gearRatio : int[];        //Shift gear at speed
     var spark : GameObject;        //OnCollision Spark
     var collisionSound : GameObject;    //OnCollision Sound
     private var axisH: float = 0;
     private var axisV: float = 0;
     
     function Start () {
     rigidbody.centerOfMass=centerOfMass; //Center of mass , for this the car should be pointing on z axis
     }
     
     function FixedUpdate () {
     HandBrake();
     }
     function Update(){
     BackLight ();
     EngineSound();
     CalculateSpeed();
     
          
     }
     
     
     function CalculateSpeed(){
     currentSpeed = 2*22/7*dataWheel.radius*dataWheel.rpm*60/1000;
     currentSpeed = Mathf.Round(currentSpeed);
     }
     
     
     function BackLight (){
     if (currentSpeed > 0 && Input.GetAxis("Vertical")<0&&!braked){
     backLightObject.renderer.material = brakeLightMaterial;
     }
     else if (currentSpeed < 0 && Input.GetAxis("Vertical")>0&&!braked){
     backLightObject.renderer.material = brakeLightMaterial;
     }
     else if (currentSpeed < 0 && Input.GetAxis("Vertical")<0&&!braked){
     backLightObject.renderer.material = reverseLightMaterial;
     }
     else if (!braked){
     backLightObject.renderer.material = idleLightMaterial;
     }
     }
     
     
     function HandBrake(){
     if (Input.GetButton("Jump")){
     braked = true;
     }
     else{
     braked = false;
     }
     }
     
     
     function EngineSound(){
     for (var i = 0; i < gearRatio.length; i++){
     if(gearRatio[i]> currentSpeed){
     break;
     }
     }
     var gearMinValue : float = 0.00;
     var gearMaxValue : float = 0.00;
     if (i == 0){
     gearMinValue = 0;
     }
     else {
     gearMinValue = gearRatio[i-1];
     }
     gearMaxValue = gearRatio[i];
     var enginePitch : float = ((currentSpeed - gearMinValue)/(gearMaxValue - gearMinValue))+1;
     audio.pitch = enginePitch;
     }
     
     function InputGetAxis(axis: String): float {
      
         var v = Input.GetAxis(axis);
         if (Mathf.Abs(v) > 0.005) return v;
         if (axis=="Horizontal") return axisH;
         if (axis=="Vertical") return axisV;
        } 
     
     
     function OnGUI (){
     GUI.DrawTexture(Rect(Screen.width - 300,Screen.height - 150,300,150),speedOMeterDial);
     var speedFactor : float = currentSpeed / topSpeed;
     var rotationAngle : float;
     if (currentSpeed >= 0){
       rotationAngle = Mathf.Lerp(0,180,speedFactor);
       }
       else {
       rotationAngle = Mathf.Lerp(0,180,-speedFactor);
       }
     GUIUtility.RotateAroundPivot(rotationAngle,Vector2(Screen.width - 150 ,Screen.height));
     GUI.DrawTexture(Rect(Screen.width - 300,Screen.height - 150,300,300),speedOMeterPointer);
     
     axisV = axisH = 0;
         if (GUI.RepeatButton( Rect( 10, 435, 100, 35 ), "Forward" ) ) axisV = 1;
         if (GUI.RepeatButton( Rect( 690, 435, 100, 35 ), "Backward" ) ) axisV = -1;
     }
     
     
     function OnCollisionEnter (other : Collision){
     
     if (other.transform != transform && other.contacts.length != 0){
     for (var i = 0; i < other.contacts.length ; i++){
     Instantiate(spark,other.contacts[i].point,Quaternion.identity);
     var clone : GameObject = Instantiate(collisionSound,other.contacts[i].point,Quaternion.identity);
     clone.transform.parent = transform;
     }
     }
     }
     
     function OnDrawGizmos  () {
             Gizmos.color = Color.white;
             Gizmos.DrawWireSphere (transform.position+centerOfMass, 0.1);
         }

Does anyone knows how to use the gui buttons as input get axis, or how to convert this script to use natively acelerometer for steering and buttons for acelerate, brake/reverse, and hand brake?