Is a wake up style alarm possible without extensions? Alarms sounding while out of the app

I've found a lot of examples of wake up alarm apps, but really only guidance to use extensions to make it work like a wake up alarm rather than a timer alarm. Is it possible to do it without any form of extension? It being sound an alarm while the app isn't in focus, even better if not open/pushed to background.

I use the built-in android/google clock / alarm.... :wink:

Simple answer, without extensions, no.