It’s a way to avoid using your private key (nsec) in a bunch of places. All of your data that you’ve posted on nostr is protected by that key. Inevitably clients will have security accidents where private keys leak. nsecBunker allows you to create “keys” for different clients, without giving those clients your private key.
I want to try out a couple of mobile clients so I can’t use the Alby or nos2x browser extensions. That’s why I’m trying to set it up.