Could be cool to run an app on #[2]​ that will filter events that are related to the user’s public key, and call an api that would send a push-notification to #[3]​ : “You have a new nostr message/mention” (without the content).

The #[4]​ and #[5]​ apps could be linked via some random uuid (includes in the api), so at no stage Apple’s server or any 3rd party could know the user’s public key.