Clearly, a Last.fm account is required for this app to work: http://www.last.fm/join
* Love, unlove, tag and untag in an elegant, material-design gui
* Ability to go back through recently-scrobbled history to edit tags / loves
* Love Widget, providing a single-click method for loving the currently playing track
* Tag Widget, pops open a window for loving / tagging currently playing track
The app is open source: https://github.com/spookypeanut/Love-Tag
I wish it was more integrated, and a little bit more style. But it does the job.