Jeffery Priddy
Let's see.

The current song thing: I'm not sure about WMP; I use Winamp. If I were rolling my own, I'd use tlist (like ps) to get Winamp's title bar text, which would include the current song. Just parse out the playlist number and the Winamp title. It wouldn't surprise me if there were little applets or plugins to export this info from Winmap or WMP, but I haven't looked.

Prompting yourself for what you're currently doing would be easy. It's not hard to ask Windows what task currently has focus, so you could automate a variation of that, naming the app you currently have forward.

As for logon status, I have a freebie from sysinternals called psloggedon which shows who's logged on locally and who's accessing files or pipes through the network. There are a lot of other ways to do this, but this is what I would use.

The idle time: Well, I had an elaborate scheme cooked up to do this, based on the Task Scheduler, and it's ability to start any task after x minutes of idle time (usefull, eh?). But then my curiosity got the best of me, and I peeked thru Google to see if I could find anything better. I found a COM object for use with WSH that returns idle time straight up, so all my machinations seemed overly complicated. I could describe it, if you were curious, but now I'd just use this add-on.

Finally, someone answered your question... :-)