Regarding the downloading of torrents. I actually started on something similar a long time ago but never completed it (not for the plugin)
Here is the API definition if you want to start taking a look
UDP API Definition - AniDB
Basically the way I planned to do it was as follows
1. Use NOTIFYLIST and NOTIFYGET to find out any new files which have been released
2. Use the FileID from above and issue a FILE command to get info about that file
3. The above will contain a CRC, using this CRC you can look at something like the Tokyo Toshokan RSS feed
In the files for most anime they have an 8 character string in square brackets which is the CRC. This is not done by all groups though.
This might be a good feature to add once i release the source code. Obviously the plugin already uses the FILE command. Also I already wrote an RSS parser, as i was planning to have some optional news in the main page, but haven't finished it off yet.