Add documentation on using Simplisafe secret alerts in triggers (#35640)

* Add documentation on using Simplisafe secret alerts in automation triggers

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Co-authored-by: c0ffeeca7 <38767475+c0ffeeca7@users.noreply.github.com>

source/_integrations/simplisafe.markdown

@@ -153,6 +153,30 @@ triggers:
         last_event_type: doorbell_detected
 ```
 
+### Using secret alerts for sensor changes
+
+For cases where the default {% term polling %} interval of 30 seconds is too long for automations, you can use secret alerts to get push notifications of a sensor being triggered.
+
+To enable secret alerts for sensor changes, follow these steps:
+
+1. Enable the secret alert for the device in the Simplisafe App.
+2. Make a note of the serial number of the device.
+    - You can see it in the top-left corner of the page where you set the alert.
+3. Use the following event trigger:
+
+  ```yaml
+  triggers:
+    - trigger: event
+      event_type: SIMPLISAFE_EVENT
+      event_data:
+          last_event_type: secret_alert_triggered
+          last_event_sensor_serial: "abc123xyz"  # Replace with your device's serial number (use lowercase letters)
+  ```
+
+{% note %}
+Due to the way Simplisafe implements secret alerts, you can only determine when a sensor is triggered, not when it is cleared.
+{% endnote %}
+
 ### `SIMPLISAFE_NOTIFICATION`
 
 `SIMPLISAFE_NOTIFICATION` events represent system notifications that would appear in the