In OS 9, you were able to turn control panels and extensions on and off using Location Manager. Don't know of anything like that in X. Still, Apple implemented it once, so maybe they'll do it later in the system development cycle.
Best you can do is "show bluetooth status in menu bar" which will allow you to turn bluetooth on and off a little bit quicker than going to Sys Prefs. My menu bar is a little crowded, so I just slog through Prefs.