I can't get the current version, 7.x-2.0-rc4, (https://drupal.org/node/2220291) to make an alias that I can use from my host into my vagrant, but the 7.x-1.0-alpha4 version works just fine after I patched it (https://www.drupal.org/node/2398349). Here's how to do it.
drush dl drush-vagrant-7.x-1.0-alpha4 // This adds the drush-vagrant directory // to your ~/.drush directory
Save my patch to your ~/.drush/drush-vagrant directory. From ~/.drush/drush-vagrant run:
git apply < 0001-checks-if-line-is-not-empty-before-adding-o.patch.txt
vagrant up vagrant ssh-config // This command prints information that you will use // with the drush vagrant script.
drush vagrant // Answer the questions. // You can include http://... in the URI question.
Copy the results into ~/.drush/aliases.drushrc.php and Voila! You can now drush from your host into your Vagrant using the alias like so:
drush @my_alias status