You can send notifications with PWAs with Web Push API + Service Worker, same as a regular page.
But, AFAIK, you need the server for push, though. It used to be possible to program entirely from the client with this proposed feature but AFAIK it's abandoned: https://github.com/GoogleChrome/developer.chrome.com//blob/m...
> You can send notifications with PWAs with Web Push API + Service Worker, same as a regular page.
While the app is awake, sure.
I'd like notifications to work even if the OS backgrounded the app, and even without a network connection, like I'd expect a reminder to work.
> https://github.com/GoogleChrome/developer.chrome.com//blob/m...
Looks like this is what I need and it doesn't exist. So the short answer is "no". Thanks for the link!