There is a built-in notifier app. My biggest issue with it, is the message are not "check-able" in the app. What I mean is the Hub will send you an alert, but if you cannot read it in the tiny window it gives you when you click on it, it opens the app and the notification is not available.
I prefer to use @Cobra email notifier must register free for his site to send email to SMS for cell phone alerts.
For audio alerts ("kitchen door is ajar") I use @tonesto7 Echo speaks and have it come out of all our Echo devices.
For dashboard alerts I use @bptworld Follow Me.
There are many options both built in, and third party. I'm sure you'll get lots of suggestions. Mine would be to review them all, and pick the ones that work best for you, your use case, and your family.