I am in the middle of completing another last.fm related plugin so the best I can say is that when Im done with that, I will *look at* pursuing the other.
I'll be honest though and say that I have always been hesitant to publiize the code. THAT has been one feature of my site that I've not wanted to share simply because it's quite customized, works perfectly for me, and is, most importantly, unique.
If I give away all the backend things that make my site mine, its no longer mine.
I obviously wouldnt object to anyone else figuring it out and publicizing it .. but Im not sure I want to.
Again, when Im done with this next plugin, (by next weekend), I'll consider this.
martinhipp, thanks but no thanks. My problem isnt with how to turn it into a plugin. :P
In the meantime, I'll point out that alex kings "since last visit" plugin could prolly do something very similar with a little modification. That ought to atleast get ppl thinking about alternate sources.