Hi all,
I've been working on a solution to a specific problem we have here in
the office - installation of machines that are not on a network which
can see my Foreman server.
To solve this, I've written a little preseed proxy in Sinatra which
sits on a public URL, and retrieves data from Foreman as the
installation client needs it. It handles the
unattended/{provision|finish|built} URLs, as well as managing the
puppet certificates. It's only been tested with Debian installations,
but there's no reason any other sort of template shouldn't work.
It's definitely an alpha release, but it works for us, so I thought
I'd put it up on Github for others to play with. There's a reasonably
comprehensive README on getting it set up, how it works, and what the
gotchas are. Main gotcha is that quite a lot of stuff is currently
hardcoded (that's for version 0.0.2 :P), so have a read through the
README and the code.
You can get the module at
https://github.com/GregSutcliffe/puppet-preseedproxy and I'd love to
hear if it helps anyone else out. Pull requests are welcome too, of
course 
Cheers,
Greg