Eu quero escrever o código de como desbloquear o telefone Android programaticament

Quero bloquear ou desbloquear o telefone quando o usuário tocar no sensor de proximidad

public class MyActivity extends Activity{   

    private static final String ACTION = "android.intent.action.ACTION_SCREEN_OFF";
    BroadcastReceiver myReceiver;
    Context context;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        context = this;
        final IntentFilter theFilter = new IntentFilter();
        theFilter.addAction(ACTION);

        context.registerReceiver(myReceiver, theFilter);
        System.out.println("inside increate");
        myReceiver = new BroadcastReceiver(){

            @Override
            public void onReceive(Context context, Intent intent) {
                // TODO Auto-generated method stub      
                    System.out.println("phone locked*****");                
            }

        };   

    }}