You have your Rails Apps with specific Gemsets in RVM.
The following commands creates a wrapped unicorn_rails bin. Be sure to replace the variables and that you have unicorn in your bundle.
rvmsudo rvm wrapper [RUBY VERSION]@[GEMSET] [GEMSET] unicorn_rails
Now you have a /usr/local/rvm/bin/[GEMSET]_unicorn_rails I will refer to [GEMSET]_unicorn_rails as [WRAPPED_NAME]
Create the other files now, especially /etc/init.d/unicorn_init
sudo update-rc.d unicorn_init defaults