actually the best device I have seen yet was in the bavarian autosports catalog.

You fill this pump with fresh brake fluid. You attach it to the master cylinder. Then you pressurize it. Then by yourself you go to each valve, one by one and open it and close it when it's nothing but fresh fluid. The pressure in the container will force fresh fluid no air into your lines. It's nice you don't have to do the tradiotional pedal pumping with this set up.
I would get it if I could be sure that it would fit more than just one car or just bimmers.