The VRbot voice recognition system looks pretty good. It support multilingual speaker independent commands in American English, Italian, Japanese and German. Francophones will have to use the 32 user defined speaker dependent commands.
action, move, turn, run, look, attack, stop, hello
left, right, up, down, forward, backward
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
The VRbot module supports 3.3-5V power, and comes with a microphone. The communications protocol is over TTL level serial and looks fairly easy to interface with a microcontroller. The demo videos give an extensive overview of working with the module and provide a good example of its real world performance.