RelativeLayout center vertical

use

 android:layout_centerVertical="true"

I have edited your layout. Check this code now.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="#33B5E5"
android:padding="5dp" >

<ImageView
    android:id="@+id/icon"
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:layout_alignParentLeft="true"
    android:layout_centerInParent="true"
    android:background="@android:drawable/ic_lock_lock" />

<TextView
    android:id="@+id/func_text"
    android:layout_width="wrap_content"
    android:layout_height="100dp"
    android:layout_gravity="center_vertical"
    android:layout_toRightOf="@+id/icon"
    android:gravity="center"
    android:padding="5dp"
    android:text="This is my test string............"
    android:textColor="#FFFFFF" />

<ImageView
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:layout_alignParentRight="true"
    android:layout_centerInParent="true"
    android:layout_gravity="center_vertical"
    android:src="@android:drawable/ic_media_next" />

</RelativeLayout>