How to create a event using acclerometer for sensing the rotation in z direction: Up and Down seprately.

For example : while holding the phone in landscape mode if bump/jerk my phone down ward in z axis than a event should be called and if i bump/jerk my phone upward in z axis another event is called. Any help would be appreciated.

I think you need to create your own event handler…

using UnityEngine;
using System.Collections;

public class Accelerometer : MonoBehaviour {

	private Vector3 _currentAcceleration;
	private Vector3 _noAcceleration;
	private float   _acceleration = 0;

    void Start() {
      _noAcceleration = Input.acceleration;
    }

	void Update () {

		_currentAcceleration = Vector3.Lerp(_currentAcceleration, Input.acceleration - _noAcceleration, Time.deltaTime / 0.5f);
		_acceleration = Mathf.Clamp(_currentAcceleration.y * 10, -1, 1);

		if (_acceleration > 0) {
			// Go UP
		} else if (_acceleration < 0) {
			// Go Down
		}
	}

	// You can also get it from other Script with a Getter/Setter
	public bool UP {
		get { return ((_acceleration > 0 ) ?  true :  false);  }
	}

	public bool Down {
		get { return ((_acceleration < 0 ) ?  true :  false);  }
	}
}

I think I will do somthings like that.