Okamoto Hidetaka

This plugin gives you Related Item Widget and function.
If you want to show Related Item List, you can do following actions:
<ul>
<li>Add <code>Elasticommerce Related Widgets</code> in your widgets area.</li>
<li>Add <code>escr_related_item();</code> function in your theme or plugins.</li>
<li>If you only want to get the data, you can use <code>escr_get_related_item();</code> function.</li>
</ul>
Notice 
This plugin requires WooCommerce Plugin , so please install it. If WooCommerce Plugin is not installed or activated, this plugin will not work.
Required 
This Plugin cannot use Elasticsearch version 2.x. Please use Elasticsearch version 1.5 instead.

Elasticommerce Related Items

You can get good Related Item List powered by Elasticsearch.

denisrcmnd

Recommend Marketing is a flexible and easy to use integration plugin that allows you to integrate your Woocommerce store with Recommend platform using Recommend API service.
Input your Recommend Marketing API key and select the mode of operation. Find your API Key within the Integration module in Recommend.
The plugin integrates into woocommerce hooks on the product page, cart, payment and payment confirmation.
By using additional parameters in the product link, the plugin catches campaigns on the Recommend platform.
After a successful product purchase, the plugin communicates with the Recommend API service and checks for conversions.
If you are testing plugin set “Testing?” checkbox to true. In testing mode, plugin will send referral check after adding product to cart.

Recommend Marketing, Integration Plugin

Recommend Marketing is an integration referral plugin for WordPress, integrated with the Woocommerce shop and based on an external API service.

Elasticommerce Related Items vs Recommend Marketing, Integration Plugin