At first great tool. It is actually the first Linux backup program I have found which has a progress bar and is working/maintained.
I am planning to add a script which starts a gui backup when a special usb drive is connected. To do this pybackpack needs some command line parameters to choose the profile and start backup or something like that.
This isn't needed of course if pybackpack would stay in tray and could do a similar thing ;) . Btw. I wouldn't make a cron service out of it. There are enough tools out there for operations like that e.g. sbackup or similar. I think it is the advantage of pybackpack that it is run in userspace with a progress bar, status messages and no needed root password. An autostart entry with systray functionality would be great of course but no cron/backend/server thing imho.