I'll admit my main use-case here is music

I guess the starting point is determining how the home-screen launches an application based on keyboard input. It obviously launches phone given number or star-hash input, and Contacts Search given ASCII input.

Curiously nothing happens when symbols like _ or & are pressed. Seems like a good opportunity to overload those keys for other functions, like a music search or a twitter search.

Is there a media-player command line that will open the album/playlist/song-search menu? Map that to _, and then I can type albums to my hearts' content and solve this issue without any real code

Might be a hildon-home mod+rebuild though, along with some gconf trickery.