diff --git a/serial.inc b/serial.inc
index 28e12a3..e11cd7f 100644
--- a/serial.inc
+++ b/serial.inc
@@ -41,29 +41,31 @@ function _serial_drop_table(array $field, array $instance) {
 }
 
 /**
- * Renames serial table(s) when a content type us renamed.
- *
- * @param string $old_type
- *   An old node type machine name.
- * @param string $new_type
- *   A new node type machine name.
+ * Renames serial table(s) when a entity bundle us renamed.
+ *
+ * @param string $entity_type
+ *   Type of entity.
+ * @param string $bundle_old
+ *   An old entity bundle machine name.
+ * @param string $bundle_new
+ *   A new entity bundle machine name.
  */
-function _serial_rename_tables($old_type, $new_type) {
+function _serial_rename_tables($entity_type, $bundle_old, $bundle_new) {
   // Build the query to find all affected tables.
   $query = db_select('field_config', 'f')
     ->fields('f', array('field_name'));
 
-  $query->join(
-    'field_config_instance',
-    'i',
-    "f.field_name = i.field_name AND f.type = 'serial' AND i.bundle = '$new_type'"
-  );
+  $query->join('field_config_instance', 'i', '(f.field_name = i.field_name)');
+
+  $query->condition('f.type', 'serial');
+  $query->condition('i.entity_type', $entity_type);
+  $query->condition('i.bundle', $bundle_new);
 
   // Rename each affected table.
   foreach ($query->addTag('node_access')->execute() as $record) {
     db_rename_table(
-      _serial_get_table_name($old_type, $record->field_name),
-      _serial_get_table_name($new_type, $record->field_name)
+      _serial_get_table_name($entity_type, $bundle_old, $record->field_name),
+      _serial_get_table_name($entity_type, $bundle_new, $record->field_name)
     );
   }
 }
@@ -80,22 +82,24 @@ function _serial_rename_tables($old_type, $new_type) {
  *   The name of the assistant table of the specified field instance.
  */
 function _serial_get_field_table_name(array $field, array $instance) {
-  return _serial_get_table_name($instance['bundle'], $field['field_name']);
+  return _serial_get_table_name($instance['entity_type'], $instance['bundle'], $field['field_name']);
 }
 
 /**
  * Gets the name of the assistant table for a specific field.
  *
+ * @param string $entity_type
+ *   Type of entity (e.g. node)
  * @param string $bundle
- *   The name of the entity type that contains the field.
+ *   The name of the entity type that contains the field (e.g. content type)
  * @param string $field_name
  *   The name of the field.
  *
  * @return string
- *   the name of the assistant table of the specified field.
+ *   The name of the assistant table of the specified field.
  */
-function _serial_get_table_name($bundle, $field_name) {
-  return db_escape_table('serial_' . $bundle . '_' . $field_name);
+function _serial_get_table_name($entity_type, $bundle, $field_name) {
+  return db_escape_table("serial_{$entity_type}_{$bundle}_{$field_name}");
 }
 
 /**
@@ -109,16 +113,17 @@ function _serial_get_table_schema() {
     'fields' => array(
       'sid' => array(
         'type' => 'serial',
-        'unsigned' => TRUE,
         'not null' => TRUE,
+        'unsigned' => TRUE,
         'description' => 'The atomic serial field.',
       ),
       'uniqid' => array(
-        'description' => 'Unique temporary allocation Id.',
         'type' => 'varchar',
         'length' => 23,
+        'default' => '',
         'not null' => TRUE,
-        'default' => ''),
+        'description' => 'Unique temporary allocation Id.',
+      ),
     ),
     'primary key' => array('sid'),
     'unique keys' => array(
@@ -128,8 +133,10 @@ function _serial_get_table_schema() {
 }
 
 /**
- * Generates a unique serial value (unique per node type).
+ * Generates a unique serial value (unique per entity bundle).
  *
+ * @param string $entity_type
+ *   Type of entity (e.g. node)
  * @param string $bundle
  *   Containing bundle (e.g. content type).
  * @param string $field_name
@@ -140,10 +147,9 @@ function _serial_get_table_schema() {
  * @return int
  *   the unique serial value number.
  */
-function _serial_generate_value($bundle, $field_name, $delete = TRUE) {
+function _serial_generate_value($entity_type, $bundle, $field_name, $delete = TRUE) {
   // Get the name of the relevant table.
-  $table = _serial_get_table_name($bundle, $field_name);
-
+  $table = _serial_get_table_name($entity_type, $bundle, $field_name);
   // Insert a temporary record to get a new unique serial value.
   $uniqid = uniqid('', TRUE);
   $sid = db_insert($table)
@@ -165,49 +171,65 @@ function _serial_generate_value($bundle, $field_name, $delete = TRUE) {
 }
 
 /**
- * Initializes the value of a new serial field in existing nodes.
- *
- * @todo Currently works only for nodes - should support comments and users.
+ * Initializes the value of a new serial field in existing entities.
  *
+ * @param string $entity_type
+ *   Type of entity (e.g. node)
  * @param string $bundle
  *   Containing bundle (e.g. content type).
  * @param string $field_name
  *   The field name.
  *
  * @return int
- *   Number of existing nodes that have been initialized.
+ *   Number of existing entities that have been initialized.
  */
-function _serial_init_old_nodes($bundle, $field_name) {
-  $nodes = node_load_multiple(array(), array('type' => $bundle));
-
-  // Allocate a serial number for every old node.
-  foreach ($nodes as $node) {
-    $node->{$field_name} = array(
-      LANGUAGE_NONE => array(
-        array(
-          'value' => _serial_generate_value($bundle, $field_name, FALSE),
+function _serial_init_old_entities($entity_type, $bundle, $field_name) {
+  $query = new EntityFieldQuery();
+  $query->entityCondition('entity_type', $entity_type)
+    ->fieldCondition($field_name);
+
+  // The "comment" entity type does not support bundle conditions.
+  // @see https://api.drupal.org/api/drupal/includes!entity.inc/function/EntityFieldQuery%3A%3AentityCondition/7
+  if ('comment' !== $entity_type) {
+    $query->entityCondition('bundle', $bundle);
+  }
+
+  $results = $query->execute();
+
+  if (!empty($results[$entity_type])) {
+    foreach ($results[$entity_type] as $entity) {
+      list($id, , $bundle) = entity_extract_ids($entity_type, $entity);
+
+      $entity = entity_load_unchanged($entity_type, $id);
+      $entity->{$field_name} = array(
+        LANGUAGE_NONE => array(
+          array(
+            'value' => _serial_generate_value($entity_type, $bundle, $field_name, FALSE),
+          ),
         ),
-      ),
-    );
+      );
 
-    node_save($node);
+      field_attach_insert($entity_type, $entity);
+    }
+
+    return count($results[$entity_type]);
   }
 
-  // Return the number of existing nodes that have been initialized.
-  return count($nodes);
+  return 0;
 }
 
 /**
  * Retrieves all the managed serial fields.
  *
- * @return array
- *   Pairs of node type name, field name.
+ * @return string[]
+ *   Result set containing entity type, entity bundle, field name.
  */
 function _serial_get_all_fields() {
   $query = db_select('field_config', 'f');
   $query->join('field_config_instance', 'i', 'i.field_name = f.field_name');
 
-  return $query->fields('i', array('bundle', 'field_name'))
+  return $query
+    ->fields('i', array('entity_type', 'bundle', 'field_name'))
     ->condition('f.type', 'serial')
     ->condition('i.deleted', 0)
     ->execute()
diff --git a/serial.info b/serial.info
index 27df301..d25f723 100644
--- a/serial.info
+++ b/serial.info
@@ -2,6 +2,5 @@ name = Serial
 description = Defines atomic auto increment (serial) field type.
 package = Fields
 core = 7.x
-dependencies[] = field
-files[] = serial.module
 
+dependencies[] = field
diff --git a/serial.install b/serial.install
index e3abdcf..7bb9231 100644
--- a/serial.install
+++ b/serial.install
@@ -37,7 +37,7 @@ function serial_schema() {
   $schema = array();
 
   foreach (_serial_get_all_fields() as $field) {
-    $schema[_serial_get_table_name($field->bundle, $field->field_name)] = $table_schema;
+    $schema[_serial_get_table_name($field->entity_type, $field->bundle, $field->field_name)] = $table_schema;
   }
 
   // Return the schema of all the assistant tables (one per field instance).
@@ -57,7 +57,7 @@ function serial_update_7130() {
   // Update the schema of old assistant tables.
   foreach (_serial_get_all_fields() as $field) {
     // Empty the table.
-    $table = _serial_get_table_name($field->bundle, $field->field_name);
+    $table = _serial_get_table_name($field->entity_type, $field->bundle, $field->field_name);
     db_delete($table)->execute();
 
     // Drop nid field and key.
@@ -69,3 +69,17 @@ function serial_update_7130() {
     db_add_unique_key($table, 'uniqid', array('uniqid'));
   }
 }
+
+/**
+ * Add 'node_' to all existing serial tables.
+ *
+ * Change name:
+ *   from: serial_{content_type}_{field_name}
+ *   to: serial_node_{content_type}_{field_name}
+ */
+function serial_update_7131() {
+  // All old serial tables are of 'node' entity type.
+  foreach (db_find_tables('serial_%') as $table) {
+    db_rename_table($table, preg_replace('/^serial_/', 'serial_node_', $table));
+  }
+}
diff --git a/serial.module b/serial.module
index 9567fab..079018b 100644
--- a/serial.module
+++ b/serial.module
@@ -24,7 +24,7 @@ function serial_field_info() {
 /**
  * Implements hook_field_create_instance().
  */
-function serial_field_create_instance($instance) {
+function serial_field_create_instance(array $instance) {
   $field = field_read_field($instance['field_name']);
 
   if ('serial' == $field['type']) {
@@ -33,10 +33,10 @@ function serial_field_create_instance($instance) {
     _serial_create_table($field, $instance);
 
     // Set serial values for old objects.
-    $old_count = _serial_init_old_nodes($instance['bundle'], $field['field_name']);
+    $old_count = _serial_init_old_entities($instance['entity_type'], $instance['bundle'], $field['field_name']);
 
     if ($old_count > 0) {
-      drupal_set_message(t('Serial values have been automatically set for %count existing nodes.', array(
+      drupal_set_message(t('Serial values have been automatically set for %count existing entities.', array(
         '%count' => $old_count,
       )));
     }
@@ -46,7 +46,7 @@ function serial_field_create_instance($instance) {
 /**
  * Implements hook_field_delete_instance().
  */
-function serial_field_delete_instance($instance) {
+function serial_field_delete_instance(array $instance) {
   $field = field_read_field($instance['field_name']);
 
   if ('serial' == $field['type']) {
@@ -59,7 +59,7 @@ function serial_field_delete_instance($instance) {
 /**
  * Implements hook_form_alter().
  */
-function serial_form_alter(&$form, $form_state, $form_id) {
+function serial_form_alter(array &$form, array &$form_state, $form_id) {
   if ('field_ui_field_settings_form' == $form_id && 'serial' == $form['field']['type']['#value']) {
     drupal_set_message(t('Serial field %field has been created.', array(
       '%field' => $form['field']['field_name']['#value'],
@@ -72,11 +72,15 @@ function serial_form_alter(&$form, $form_state, $form_id) {
 /**
  * Implements hook_field_presave().
  */
-function serial_field_presave($entity_type, $entity, $field, $instance, $langcode, &$items) {
+function serial_field_presave($entity_type, $entity, array $field, array $instance, $langcode, array &$items) {
   if (empty($items)) {
     module_load_include('inc', 'serial');
 
-    $items = array(array('value' => _serial_generate_value($instance['bundle'], $field['field_name'])));
+    $items = array(
+      array(
+        'value' => _serial_generate_value($entity_type, $instance['bundle'], $field['field_name']),
+      ),
+    );
   }
 }
 
@@ -100,13 +104,12 @@ function serial_node_presave($node) {
 }
 
 /**
- * Implements hook_node_type_update().
+ * Implements hook_field_attach_rename_bundle().
  */
-function serial_node_type_update($info) {
-  // Handle content type rename:
-  if (isset($info->old_type) && ($info->old_type != $info->type)) {
+function serial_field_attach_rename_bundle($entity_type, $bundle_old, $bundle_new) {
+  if ($bundle_old !== $bundle_new) {
     module_load_include('inc', 'serial');
-    _serial_rename_tables($info->old_type, $info->type);
+    _serial_rename_tables($entity_type, $bundle_old, $bundle_new);
   }
 }
 
@@ -125,7 +128,7 @@ function serial_field_formatter_info() {
 /**
  * Implements hook_field_formatter_view().
  */
-function serial_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, $items, $display) {
+function serial_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, array $items, $display) {
   $element = array();
 
   // Define the field contents for the single default formatter.
@@ -157,7 +160,7 @@ function serial_theme() {
 /**
  * Theme function for the default formatter.
  */
-function theme_serial_formatter_default($variables) {
+function theme_serial_formatter_default(array $variables) {
   return $variables['serial_id'];
 }
 
@@ -176,7 +179,7 @@ function serial_field_widget_info() {
 /**
  * Implements hook_field_widget().
  */
-function serial_field_widget(&$form, &$form_state, $field, $instance, $items, $delta = 0) {
+function serial_field_widget(array &$form, array &$form_state, array $field, array $instance, array $items, $delta = 0) {
   return array(
     'value' => array(
       '#type' => 'hidden',
@@ -184,3 +187,45 @@ function serial_field_widget(&$form, &$form_state, $field, $instance, $items, $d
     ),
   );
 }
+
+/**
+ * Implements hook_tokens().
+ *
+ * Replace token for generic entity type.
+ */
+function serial_tokens($type, array $tokens, array $data = array(), array $options = array()) {
+  $entity_info = entity_get_info($type);
+  $replacements = array();
+
+  if (empty($entity_info) || empty($data[$type])) {
+    return $replacements;
+  }
+
+  list(, , $bundle) = entity_extract_ids($type, $data[$type]);
+  $pathauto = module_exists('pathauto');
+
+  foreach ($tokens as $name => $original) {
+    // Convert token to field name.
+    $field_name = str_replace('-', '_', $name);
+    $field_info = field_info_field($field_name);
+
+    if ('serial' === $field_info['type']) {
+      continue;
+    }
+
+    if ($pathauto && strpos(pathauto_pattern_load_by_entity($type, $bundle), "$type:$field_name") !== FALSE) {
+      continue;
+    }
+
+    /* @var array $items */
+    $items = field_get_items($type, $data[$type], $field_name);
+
+    if (empty($items)) {
+      continue;
+    }
+
+    $replacements[$original] = $items[0]['value'];
+  }
+
+  return $replacements;
+}