Drupal Entity API: Get field value

function get_entity_field_value($entity_id, $field_name, $entity_type = 'node') {
    $entity = entity_load($entity_type, $entity_id);
    $field_items = field_get_items('node', $entity, $field_name);
    $field_values = array();
    foreach ($field_items as $field_item) {
        $field_value = field_view_value('node', $entity, $field_name, $field_item);
        $field_values[] = render($field_value);
    }
    return implode('', $field_values);
}