Being able to scrobble tracks played through Slacker Radio would be great. Is that possible?

Hi, yes it is certainly possible, but it would require some small changes by the developers of Slacker Radio. You could contact them and tell them about SLS, and how easy it is to enable scrobbling (it's all here: http://code.google.com/p/a-simple-lastfm-scrobbler/wiki/Developers )

I'd be happy to answer any questions you or they might have.

Thanks for the feedback!