Nice!
I've seen this in Synaptic's software list, but never bothered to try it. I don't know that I have any apps I need to stay open all the time, and if I do, I usually keep them on an out-of-the-way virtual window.
I just wish Fluxbox's tray/taskbar wasn't so tiny. It'd make trayed items easier to get at if the size was customizable (i've looked, couldn't find a config item for it...).