* Listen on specific interfaces or protocols (eg. only IPv6).

* Can we do language bindings using #!'s?
  You would enter:
    nbdkit foo [args]
  where nbdkit-foo-plugin is a Perl script starting:
    #!perl
  which causes nbdkit to load the perl plugin wrapper.

* syslog? journal?

* Glance and/or cinder plugins.

* Performance - measure and improve it.
