Yay got them all working nicely together. In this shot, the top-right window is the Tomboy note-taker (read: Wiki), with a page I'd stuck together containing some working-out for getting all the mono stuff onto my desktop. On the right, you can see the beagle search tool best (beagle-something-search-tool) displaying some results for the query mono (pretty unimaginative). This includes the note on the right.
On the bottom-right, you can see an in-progress chat. The minute I typed mono to Kian, the kernel inotify magic prodded beagle to let it know the file had updated, and the search results adjusted to include the chat, without having to press any other buttons.