NerdKey

Powered by NerdTools.co.uk Uptime Tracker (http://uptime.nerdtools.co.uk/) this plugin will add a widget to your sidebar that will show the percentage of availability or uptime for any website over the last 30 days.
In terms of the tracking system, checks are carried out every 5 minutes from different locations and then averages are worked out to form the overall reports from which the graph is generated and shown via an iframe.
Other reports including hourly, weekly and daily can be seen by visiting the Uptime Tracker website directly.
<h3>Arbitrary section 1</h3>

Uptime Widget

Adds a simple uptime gauge to your WordPress sidebar, showing the percentage of availability for any website over the past 30 days.

pianoweb

SentWatch monitors WordPress email delivery reliability with instant notifications when problems occur.
The plugin sends periodic “heartbeats” to our monitoring service. If these signals stop arriving, it means your site has stopped sending emails (SMTP issues, plugin conflicts, server problems), and we notify you immediately.
Key Features:
<ul>
<li>Hybrid Heartbeat System – Uses HTTP API with email fallback for maximum reliability</li>
<li>Automatic Time Sync – Plugin synchronizes with server time to prevent false alarms</li>
<li>Instant Notifications – Get alerts immediately when email delivery fails</li>
<li>Zero Configuration – Just enter your API key and you’re done</li>
<li>Lightweight – No performance impact on your site (runs in background)</li>
<li>Smart Scheduling – Heartbeats are automatically aligned with server expectations</li>
</ul>
How It Works:
<ol>
<li>Plugin sends a “heartbeat” signal at regular intervals</li>
<li>Our server tracks when heartbeats arrive</li>
<li>If a heartbeat is missed, we verify your site is reachable</li>
<li>If the issue persists, you receive an instant email notification</li>
</ol>
Subscription Plans:
<ul>
<li>Free – 1 site, 24-hour monitoring interval</li>
<li>Silver – 10 sites, 12-hour interval</li>
<li>Gold – 50 sites, 6-hour interval</li>
<li>Platinum – 200 sites, 3-hour interval</li>
</ul>
Note: This plugin requires a free account on <a href="https://panel.sentwatch.com/register.php" rel="nofollow ugc">SentWatch</a>.
<h3>External Services</h3>
This plugin connects to the SentWatch monitoring service to provide email delivery monitoring functionality.
Service Provider: SentWatch (operated by PianoWeb) 
Service URL: https://panel.sentwatch.com
What data is transmitted:
<ol>
<li>
During initial setup – When you connect the plugin with your API key:
<ul>
<li>Site URL</li>
<li>Site name</li>
<li>WordPress version</li>
<li>PHP version</li>
<li>Plugin version</li>
</ul>
</li>
<li>
During periodic heartbeats – Sent via email at intervals determined by your plan (every 3-24 hours):
<ul>
<li>Timestamp</li>
<li>Site URL</li>
<li>Plugin version</li>
</ul>
</li>
<li>
During status checks – When you view the plugin settings page or when the plugin syncs configuration:
<ul>
<li>Site UUID (unique identifier)</li>
<li>API Key (for authentication)</li>
</ul>
</li>
</ol>
When data is sent: 
– On initial plugin activation and setup 
– Periodically via scheduled email heartbeats (frequency depends on your subscription plan) 
– When you manually test email delivery 
– When the plugin checks for configuration updates (daily)
Why this data is sent: 
This data is necessary for the monitoring service to track whether your WordPress site is successfully sending emails. If heartbeat emails stop arriving, the service alerts you that your site’s email functionality may be broken.
Legal: 
– Terms of Service: https://panel.sentwatch.com/terms.php 
– Privacy Policy: https://panel.sentwatch.com/privacy.php
By using this plugin, you acknowledge that your site will communicate with the SentWatch service as described above.

SentWatch – Email Uptime Monitoring

Monitor WordPress email delivery with instant notifications when problems occur.

Uptime Widget vs SentWatch – Email Uptime Monitoring