Using Braille displays in Mac OS 10.6. (No 10.7-level documentation yet.) Macs support more than 50 Braille displays, which begin working the instant you plug them in or instantly after you pair them. And a classroom full of kids can follow along on 31 other displays.
And obviously Braille displays work instantly with iPads and iPhones. (Jim Denham of Perkins is one of the elite blind people who uses a Braille display with an iPad.) In fact, you can operate an iPhone from certain Braille displays with extra keys, like Braille notetakers.