This is a brilliant Chrome extension. Thanks so much for your efforts! I'm using it to collect song info then display that in a Rainmeter skin.
One main feature I'd like to see, if possible, is favorite/heart status on Slacker.com so that I can display it within the Rainmeter skin. I found the elements on the Slacker page which indicate the heart (#mini-heart.play-control.heart -- not favorited; #mini-heart.play-control.heart.active -- favorited), but looking at the content.js file for UNPN I've no idea how to add this ability. Other users may appreciate this feature as well, especially if support is added for more sites.
Also, it would be very nice if UNPN placed a transparent png when there's nothing playing, i.e. when it clears the song info from the stored txt file. It was trivial to create a 125x125px fully transparent png in GIMP, but I wouldn't know where to begin to have UNPN utilize it when there's nothing playing.
Thanks again to everyone who has some contribution, especially Wylk who has continued to maintain this from Untamed!