Random dev thoughts: Would it be a good idea to do an open source web push notification server for Nostr?

It could have fine-grained options for what notifications you want, from whom and how often.

It could be used automatically in the background by a client, or through its own web UI. Clicking the notifications would redirect you to the client of your choice.

It would be a lot like a relay in that it needs to match incoming events to a potentially large amount of subscriptions. Subscriptions would be persisted in a database and maybe managed over a REST API.

In addition to the stuff typically sent over Nostr, you need to send the subscription object and other things like notification frequency, maximum social graph distance or score, minimum zap amount to notify etc.

It would connect to other relays and maybe also have a websocket endpoint for receiving events over Nostr protocol.

Extending strfry into this direction crossed my mind, but maybe something like Django (or whatever web framework you're familiar with) would be better, as we need to persist the subscriptions.