Hey, sorry just saw your question. Not sure why it didn't come up in my notifications on Damus earlier.
That's a good question. So far I've only seen nos2x implement it. I'm guessing that if any client invokes the `nostr:` URL it might be handled with the extension to launch the output via the URL you've set in there.
Might also end up being useful to encode callback events into `nostr:` URL's and be handled for authentication etc..
