Hi,
Before switching to Sourcetree I was a gitx user, and also evaluated git-tower, and both of those apps feature a command line tool, to launch their app from a repository.
I found an earlier request for this at the old sourcetree site here:
http://support.sourcetreeapp.com/discussions/suggestions/126-invoking-sourcetree-from-the-command-line
However with the current version of sourcetree (1.2.81/1.2.8.1) invoking it from the command line with that command:
open $1 -a sourcetree
results in somewhat unexpected and annoying behavior. Sourcetree does not recognize repositories opened this way that already have bookmarks, so it 1) always prompts (sometimes two or three times) to create a new bookmark, and 2) it does not remember any window settings for the repository, even if you create a new bookmark from the popup.