Thanks! Tried it with (k)nsupdate, and it might be nice to add them into snippets and/or documentation. E.g., using the same placeholder names as in the documentation:
$ nsupdate # or knsupdate
> server update.dynip.dev
> zone YOUR_DOMAIN
> key hmac-md5:key-YOUR_DOMAIN YOUR_BASE64_KEY
> update add YOUR_DOMAIN. 300 IN A YOUR_IP
> send