The Android app "Home Assistant" offers besides numerous cell phone sensor values in Home Assistant also a very simple way to receive notifications from Home Assistant:https://play.google.com/store/apps/details?id=io.homeassistant.companion.android&hl=de_AT&gl=US.

Alternatively, the messenger Signal can be used for notifications, see: Send Signal messages via API: signal-cli-rest-api.

Anyone who has published Home Assistant on the internet via https can also use the HTML5 Push Notifications integration:

This allows a notification to be activated in the browser: without any additional app, purely through the browser.

Those who install the Home Assistant app will notice that Home Assistant regularly announces updating the phone sensors after Home Assistant:

Refresh Sensors.

By default, a notification with "Update sensors" is displayed every 15 minutes:

The notice can be easily removed by long pressing on the notification and disabling "SensorWorker":

Deactivating the SensorWorker does not affect the notifications stored in the automations, they still remain active. To receive a notification when an event occurs, an automation can be created for this purpose by clicking on "Configuration" and "Automation":

Notification when a certain value is reached

As an example, I created a notification for monitoring the humidity:

I created a new automation for this notification in Configuration / Automation:

The notification can be tested later with "RUN ACTIONS", but first to the settings of this automation:

service: notify.mobile_app_sm_a405fn
data:
  title: Luftfeuchtigkeit Bad
  message: >-
    Luftfeuchtigkeit: {{states('sensor.bad_2')}}%
    Temperatur:{{states('sensor.bad')}}°C

Criticism of the notification function:

Discussions about notifications in Home Assistant show that customizing and managing notifications can be complex. Many users want a standardized interface for easy control across platforms such as iOS and Android. Flexibility in the personalization of notifications and the ability to send notifications for groups or zones is seen as important to overcome the current fragmented implementation, see: https://community.home-assistant.io/t/wth-is-it-this-complicated-to-send-a-notification/802547/26

Conclusion

The Android app "Home Assistant" enables simple notifications directly from Home Assistant and the use of cell phone sensors. Alternatively, HTML5 push notifications and the messenger Signal can be used for notifications. The management and customization of these functions is perceived as complex, with the requirement for a standardized and flexible interface.