How to theme a block Drupal 7 example

how-to-hook_theme()

/**
 * Function
 */
function myfunction() {
    $variables = array(
        'message' => 'Hi Bitches!',
        'name' => 'Monk'
    );
    return theme('mobile-nav', $variables);
}
/**
 * Implements hook_theme();
 */
function ooyala_mobilenav_theme() {
    return array(
        'mobile-nav' => array(
            'template' => 'mobile-nav' //Name of the tpl should be mobile-nav.tpl.php
        ),
        'variables' => array(
            'message' => '',
            'name' => ''
        )
    );
}
//The mobile-nav.tpl.php
<h3><?php echo $message; ?> this is <?php echo $name; ?></h3>