Today I need to see the status of torrents from the terminal on the raspberry. After obtaining this information, you can implement a lot of things (turn on an LED when a torrent is finished, send an email, write something on the lcd monitor etc ...).
The solution is the following:
transmission-remote --auth=username:password -l
but if, as in my case the transmission is non-standard port or host is different just use the command
transmission-remote host:port --auth=username:password -l
After obtaining the status of the torrent you can do the "parsing" of the result to be able to implement in a script (send mail, php page, lcd, led etc ...)
For more information and options read the man transmission-remote