That one probably wouldnt be too hard too implement there is a track.love method in the last.fm API.
method details here,
http://www.last.fm/api/show?service=260
The authentication is already taken care of in subsonic all you need for the track.love method is:
track (Required) : A track name (utf8 encoded)
artist (Required) : An artist name (utf8 encoded)
api_key (Required) : A Last.fm API key.
api_sig (Required) : A Last.fm method signature. See authentication for more information.
sk (Required) : A session key generated by authenticating a user via the authentication protocol.
If the user has activated scrobbling in the subsonic options then a small button could be added next to the 'now playing' track name, i assume the call would be something like the following
http://ws.audioscrobbler.com/2.0/?metho ... y=xxx...... etc
I'd like to see this on the android app too
I appreciate this is just another thing to add to the long list of stuff, but it would be a nice touch.