I just tried using coracle with only my npub on my phone. It's mostly good but it seems to show me I have notifications, but not let me see them.

It also made me realize it would be nice to be able to write replies and posts, but in a way that they are queued up to publish once you get home/to a computer with your nsec on it. Probably would want it encrypted, NIP-04 DMs are probably "good enough" for this, the metadata leak is hardly fatal. You'd want a key handshake so that your nsec-having client knows what to do with them.

I guess this kinda looks like NIP-46 but with manual review, and persisted signing requests (and very likely you might perform an edit during review).