So I didn’t get the time I wanted to do a proper tutorial, but I think with the combination of @BobG & @rickkas7 projects this should be a pretty simple add on for “push” style notifications.
First go to https://puravidaapps.com/notification.php and download the Simple Notification add on (.aix file).
Next import it into you app inventor project by selecting the Import extension link in the Extension tab.
Add it to your project. I left all of the properties like this:
Then go to your blocks page and add it where you want to have a notification.
In this example I capture multiple Firebase data change events and call the appropriate procedure to process the data. In this case when the garage door data changed I call the notification block. One important thing to note is that the notification will only execute while your app is running. To “Close” the app without exiting it, you can hit the home button or add a button to the screen that calls the MoveTaskToBack method. The extension site has a lot of FAQs that answered pretty much all of my questions. Hope someone finds this useful!