diff --git a/CHANGELOG-3.1.md b/CHANGELOG-3.1.md
index 8880675..12fbb05 100644
--- a/CHANGELOG-3.1.md
+++ b/CHANGELOG-3.1.md
@@ -19,3 +19,5 @@ https://github.com/FriendsOfSymfony/FOSElasticaBundle/compare/v3.0.4...v3.1.0
    this class on every request where doctrine is active. #729
  * Added ability to configure `date_detection`, `numeric_detection` and
    `dynamic_date_formats` for types. #753
+ * New event `POST_TRANSFORM` which allows developers to add custom properties to
+   Elastica Documents for indexing.
diff --git a/Event/TransformEvent.php b/Event/TransformEvent.php
new file mode 100644
index 0000000..4f6871f
--- /dev/null
+++ b/Event/TransformEvent.php
@@ -0,0 +1,78 @@
+<?php
+
+/**
+ * This file is part of the FOSElasticaBundle project.
+ *
+ * (c) Infinite Networks Pty Ltd <http://www.infinite.net.au>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\ElasticaBundle\Event;
+
+use Symfony\Component\EventDispatcher\Event;
+
+class TransformEvent extends Event
+{
+    const POST_TRANSFORM = 'fos_elastica.post_transform';
+
+    /**
+     * @var mixed
+     */
+    private $document;
+
+    /**
+     * @var array
+     */
+    private $fields;
+
+    /**
+     * @var mixed
+     */
+    private $object;
+
+    /**
+     * @param mixed $document
+     * @param array $fields
+     * @param mixed $object
+     */
+    public function __construct($document, array $fields, $object)
+    {
+        $this->document = $document;
+        $this->fields = $fields;
+        $this->object = $object;
+    }
+
+    /**
+     * @return mixed
+     */
+    public function getDocument()
+    {
+        return $this->document;
+    }
+
+    /**
+     * @return array
+     */
+    public function getFields()
+    {
+        return $this->fields;
+    }
+
+    /**
+     * @return mixed
+     */
+    public function getObject()
+    {
+        return $this->object;
+    }
+
+    /**
+     * @param mixed $document
+     */
+    public function setDocument($document)
+    {
+        $this->document = $document;
+    }
+}
diff --git a/Resources/config/transformer.xml b/Resources/config/transformer.xml
index 4ce5062..0957152 100644
--- a/Resources/config/transformer.xml
+++ b/Resources/config/transformer.xml
@@ -12,7 +12,8 @@
 
     <services>
         <service id="fos_elastica.model_to_elastica_transformer" class="%fos_elastica.model_to_elastica_transformer.class%" public="false" abstract="true">
-            <argument  type="collection" /> <!-- options -->
+            <argument type="collection" /> <!-- options -->
+            <argument type="service" id="event_dispatcher" /> <!-- options -->
             <call method="setPropertyAccessor">
                 <argument type="service" id="fos_elastica.property_accessor" />
             </call>
diff --git a/Resources/doc/cookbook/custom-properties.md b/Resources/doc/cookbook/custom-properties.md
new file mode 100644
index 0000000..cc7751e
--- /dev/null
+++ b/Resources/doc/cookbook/custom-properties.md
@@ -0,0 +1,33 @@
+##### Custom Repositories
+
+Since FOSElasticaBundle 3.1.0, we now dispatch an event for each transformation of an 
+object into an Elastica document which allows you to set custom properties on the Elastica
+document for indexing.
+
+Set up an event listener or subscriber for 
+`FOS\ElasticaBundle\Event\TransformEvent::POST_TRANSFORM` to be able to inject your own
+parameters.
+
+```php
+class CustomPropertyListener implements EventSubscriberInterface
+{
+    private $anotherService;
+    
+    // ...
+    
+    public function addCustomProperty(TransformEvent $event)
+    {
+        $document = $event->getDocument();
+        $custom = $this->anotherService->calculateCustom($event->getObject());
+                    
+        $document->set('custom', $custom);
+    }
+    
+    public static function getSubscribedEvents()
+    {
+        return array(
+            TransformEvent::POST_TRANSFORM => 'addCustomProperty',
+        );
+    }
+}
+```
diff --git a/Resources/doc/index.md b/Resources/doc/index.md
index 349723b..c856798 100644
--- a/Resources/doc/index.md
+++ b/Resources/doc/index.md
@@ -13,6 +13,7 @@ Cookbook Entries
 ----------------
 
 * [Aliased Indexes](cookbook/aliased-indexes.md)
+* [Custom Indexed Properties](cookbook/custom-properties.md)
 * [Custom Repositories](cookbook/custom-repositories.md)
 * [HTTP Headers for Elastica](cookbook/elastica-client-http-headers.md)
 * Performance - [Logging](cookbook/logging.md)
diff --git a/Tests/Transformer/ModelToElasticaAutoTransformerTest.php b/Tests/Transformer/ModelToElasticaAutoTransformerTest.php
index 1fa6a8e..bb52129 100644
--- a/Tests/Transformer/ModelToElasticaAutoTransformerTest.php
+++ b/Tests/Transformer/ModelToElasticaAutoTransformerTest.php
@@ -2,6 +2,7 @@
 
 namespace FOS\ElasticaBundle\Tests\Transformer\ModelToElasticaAutoTransformer;
 
+use FOS\ElasticaBundle\Event\TransformEvent;
 use FOS\ElasticaBundle\Transformer\ModelToElasticaAutoTransformer;
 use Symfony\Component\PropertyAccess\PropertyAccess;
 
@@ -132,6 +133,21 @@ class ModelToElasticaAutoTransformerTest extends \PHPUnit_Framework_TestCase
         }
     }
 
+    public function testTransformerDispatches()
+    {
+        $dispatcher = $this->getMockBuilder('Symfony\Component\EventDispatcher\EventDispatcherInterface')
+            ->getMock();
+        $dispatcher->expects($this->once())
+            ->method('dispatch')
+            ->with(
+                TransformEvent::POST_TRANSFORM,
+                $this->isInstanceOf('FOS\ElasticaBundle\Event\TransformEvent')
+            );
+
+        $transformer = $this->getTransformer($dispatcher);
+        $transformer->transform(new POPO(), array());
+    }
+
     public function testThatCanTransformObject()
     {
         $transformer = $this->getTransformer();
@@ -295,8 +311,8 @@ class ModelToElasticaAutoTransformerTest extends \PHPUnit_Framework_TestCase
         $this->assertTrue(array_key_exists('obj', $data));
         $this->assertInternalType('array', $data['obj']);
         $this->assertEquals(array(
-             'foo' => 'foo', 
-             'bar' => 'foo', 
+             'foo' => 'foo',
+             'bar' => 'foo',
              'id' => 1
            ), $data['obj']);
     }
@@ -387,11 +403,12 @@ class ModelToElasticaAutoTransformerTest extends \PHPUnit_Framework_TestCase
     }
 
     /**
+     * @param null|\Symfony\Component\EventDispatcher\EventDispatcherInterface $dispatcher
      * @return ModelToElasticaAutoTransformer
      */
-    private function getTransformer()
+    private function getTransformer($dispatcher = null)
     {
-        $transformer = new ModelToElasticaAutoTransformer();
+        $transformer = new ModelToElasticaAutoTransformer(array(), $dispatcher);
         $transformer->setPropertyAccessor(PropertyAccess::getPropertyAccessor());
 
         return $transformer;
diff --git a/Transformer/ModelToElasticaAutoTransformer.php b/Transformer/ModelToElasticaAutoTransformer.php
index 106db15..eff29d2 100644
--- a/Transformer/ModelToElasticaAutoTransformer.php
+++ b/Transformer/ModelToElasticaAutoTransformer.php
@@ -2,6 +2,8 @@
 
 namespace FOS\ElasticaBundle\Transformer;
 
+use FOS\ElasticaBundle\Event\TransformEvent;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\PropertyAccess\PropertyAccessorInterface;
 use Elastica\Document;
 
@@ -12,6 +14,11 @@ use Elastica\Document;
  */
 class ModelToElasticaAutoTransformer implements ModelToElasticaTransformerInterface
 {
+    /**
+     * @var EventDispatcherInterface
+     */
+    protected $dispatcher;
+
     /**
      * Optional parameters
      *
@@ -32,10 +39,12 @@ class ModelToElasticaAutoTransformer implements ModelToElasticaTransformerInterf
      * Instanciates a new Mapper
      *
      * @param array $options
+     * @param EventDispatcherInterface $dispatcher
      */
-    public function __construct(array $options = array())
+    public function __construct(array $options = array(), EventDispatcherInterface $dispatcher = null)
     {
         $this->options = array_merge($this->options, $options);
+        $this->dispatcher = $dispatcher;
     }
 
     /**
@@ -92,6 +101,13 @@ class ModelToElasticaAutoTransformer implements ModelToElasticaTransformerInterf
             $document->set($key, $this->normalizeValue($value));
         }
 
+        if ($this->dispatcher) {
+            $event = new TransformEvent($document, $fields, $object);
+            $this->dispatcher->dispatch(TransformEvent::POST_TRANSFORM, $event);
+
+            $document = $event->getDocument();
+        }
+
         return $document;
     }