I'm currently using Drush Make to pull custom modules, installation profile, and various other modules/libraries when I provision a new Drupal site.
What I'd love is if I could use drush upc to update my custom modules. I'm not sure if this is possible if I provide some magic meta data to drush or include my .git with a specified remote host.
My understanding is that Drush leverages the update status module in core for this functionality so this may not necessarily be a Drush specific issue.
Any help or suggestions on where to look would be appreciated.