I tried this once. But you'll need to compile the daemon from source, but especially on the mac this is very easy .
Then just either install the daemon in a default place, or where-ever you want it, and enter that as the executable lingon (launchd). Do make sure you add it to 'Users Daemons' not as ...
You do need to enable rpc/web ui first and make sure the white-list is correct. Also, the scripts assume you have Transmission v1.42. I'm assuming the options are in the preferences, otherwise check the wiki.