smilight

Simple plugin to show wp and installed plugins info by url http://YOUR_WEBSITE/seraph-monitor/v1/info/ 
Will be useful for external WP dashboards and wp monitoring services.
Plugin will show: 
* all installed plugins on your site with short info 
* outdated plugins and boolean near plugin that needs update 
* wordpress version and boolean if wp needs update 
* all installed themes with short info 
* outdated themes and boolean near theme that needs update 
* php version installed on server 
* mysql version installed on server

SeraphConsulting monitor

Simple plugin to show wp and installed plugins info

Valice

Banner alerts are custom alerts to notify your website visitors of promotions, alerts, events, etc. These display at the top of the website until they are dismissed by the visitor. Any new visitor who has not been to the website will see these until they are dismissed.
Banner alerts are configured just like a post or page with support for title, content, and excerpt. The plugin settings allow you to define which parts of the alert to display and whether or not to link to the full post. You can run more than one alert at a time and activate or deactivate as needed.
This plugin is ideal for:
<ul>
<li>Important operational changes</li>
<li>Technical notices</li>
<li>Time-sensitive appeals for donation or action</li>
<li>Terms or agreement changes</li>
<li>Privacy notice acknowledgements</li>
<li>Service outages or maintenance messages</li>
<li>Special offers or promotions</li>
</ul>

Banner Alerts

Provides an easy interface for creating and displaying alerts or notices as a banner on a website

SeraphConsulting monitor vs Banner Alerts