Jason Judge

Allows access to custom meta fields on products through the API. 
In short, installing this plugin on your WooCommerce site, will extend the 
WooCommerce API so that custom metadata can be passed back and forth through 
that API.
See the main documentation here: https://github.com/judgej/wc-api-custom-meta

WC API Custom Meta

Awesome!

Allows access to custom meta fields on products through the API.

Akeda Bagus

This plugin is an extension to <a href="https://wordpress.org/plugins/slack" rel="ugc">Slack plugin</a> that allows you to send notifications to Slack channels whenever payment in WooCommerce is marked as complete.
The new event will be shown on integration setting with text When a payment in WooCommerce is marked as complete. If checked then notification will be delivered once payment is marked as complete.
You can alter the message with <code>slack_woocommerce_order_status_completed_message</code> filter. The filter receives following parameters (ordered by position):
<ul>
<li><code>$message</code> — Default string of message to be delivered</li>
<li><code>$order</code> — Order object</li>
</ul>
Development of this plugin is done on <a href="https://github.com/gedex/wp-slack-woocommerce" rel="nofollow ugc">GitHub</a>. Pull requests are always welcome.

Slack WooCommerce

Send notifications to Slack channels whenever payment in WooCommerce is marked as complete.

WC API Custom Meta vs Slack WooCommerce