iPhone Touch

I have written a script to control my character and i can choose whether to use the accelerometer or touch to control. What i want to do for the touch is when you hold down your finger on the phone the player will continue to go up and when you release the gravity will cause it to come back down. right now when you touch the player will go up and stay up when you release. Do i use Touch Phases? How do I do this? Thanks

var Speed : float;
var ForwardSpeed : float;
var UseAccelerometer : boolean;
var UseTouch : boolean;
var Sensitivity : float;

function FixedUpdate () 
 //PC Testing Control
 var pc_z : float = Input.GetAxis ("Vertical");
 var computerMovement : Vector3 = Vector3(0, pc_z * Sensitivity, 0);
 rigidbody.AddForce(computerMovement * Time.fixedDeltaTime * Speed);
 //iPhone Accelerometer Control
 if (UseAccelerometer)
 var mobile_z : float = Input.acceleration.x;
 var accelMovement : Vector3 = Vector3(0, mobile_z * Sensitivity, 0);
 rigidbody.AddForce(accelMovement * Time.fixedDeltaTime * Speed);
 //iPhone Touch Control
 if (UseTouch)
 var mobileTouch_z : float = Input.touchCount;
 var touchMovement : Vector3 = Vector3(0, mobileTouch_z * Sensitivity, 0);
 rigidbody.AddForce(touchMovement * Time.fixedDeltaTime * Speed);

You could use a unity GUI.button for your control, as it responds to touch input.

or you could write an checkTouch(x,y,width,height) function that loops through all touches and touch phases, and sees if any of the touches are inside the box specified

or if you dont care where you are touching on the screen, just checkā€¦
if( (touch.phase == TouchPhase.Moved) || (touch.phase == TouchPhase.Stationary))
accelerate up;
accelerate down; //gravity