This is my take of the init script system I've seen tossed around. Because I don't run RVM on servers, I have removed it in favor of assuming the user can define the correct path to unicorn themselves. If you need RVM, see the upstream version of this gist.
- Have a server with 1+ working unicorn instances with config defined in config/unicorn.rb.
- Create /etc/unicorn/[APPNAME].conf for each app on the server.
- Install init script at /etc/init.d/unicorn.
sudo update-rc.d unicorn defaults