This kind of exists right now
although its based on an esp32 so not very secure
I have it working in noStrudel on chome using web serial. But I agree we need something better.
If there is a way for web apps to connect to it I would love to add support for it in noStrudel
GitHub
GitHub - lnbits/nostr-signing-device: Signing device for Nostr
Signing device for Nostr. Contribute to lnbits/nostr-signing-device development by creating an account on GitHub.