Today I went to MacCenter to see if I could find a wireless PCI card for my B&W G3, but unfortunately they didn’t have any in stock.
I ended up buying a Griffin PowerMate. This is a very cool device – besides working as a volume control, you can also program it to do different things in each application. As a bonus, it can also act as a power on button if it’s connected directly to the computer (which I haven’t done).