try something like that :

var moveFactor : float = -Input.acceleration.y;

function Update (){

if ( moveFactor>0) {

transform.rotation.eulerAngles.y=-90;

  do something;

}else if (moveFactor<0){

transform.rotation.eulerAngles.y=90;

  do something;

}else{

do something;

}

}

i use something like that on several iOS & Android games & it works great for me

Thank to all of your answer so much... That code really help me.

All I can tell you is AccelerationEvent.deltaTime This will tell you the time since the last acceleration Lat measured acceleration - Input.acceleration

Heres an example from unity reference

// 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 // and Home button is in the right hand

// remap device acceleration axis to game coordinates: // 1) XY plane of the device is mapped onto XZ plane // 2) rotated 90 degrees around Y axis dir.x = -Input.acceleration.y; dir.z = 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.Translate (dir * speed); }