Lego builder Yaya Lu created a prototype voice-controlled wheelchair out of Lego Mindstorms NXT elements, along with such 3rd party add-ons as Rotacaster omniwheels and a Dexter Industriues NXTBee module.
One of the problems with voice command systems is that the voice commands will be different for each of the approximately 7,000 languages used on Earth. To allow my control system to be able to be used by speakers of any of these languages, I make my voice commands language-independent by using a combination of short and long sounds (“dit” and “dah”). To recognize these commands I use a second NXT computer brick (see below) with a LEGO sound sensor and an NXTBee sensor attached to send my voice commands to the wheelchair. The commands used are three “dit” or “dah” sounds. This gives a total of 8 commands. This second NXT brick is programmed in RobotC to recognize these sound commands and to type “dit” or “dah” (plus the recognized command) on to the NXT screen to enable the speaker to check that their voice command has been recognized.
The radio commands are sent from the transmitter NXTBee and are received by the second NXTBee attached to the wheelchair robot. The NXT computer brick on the wheelchair then obeys a RobotC program that translates these commands into the movements: wheelchair forwards, wheelchair backwards, wheelchair spin clockwise, wheelchair spin anti-clockwise, wheelchair sideways left, wheelchair sideways right, and wheelchair stop.
[via the NXT Step]