Hello!
I don't know of any such shield. And I would say there is some kind of contradiction
in doing such a shield. If you develop a voice recognition engine, it means you'r using
some kind of powerful ARM or DSP. Then if you need some arduino-like functionality
(IO pins, LEDs, etc...), then you can program it with the voice recognition board, so
there is no point in having arduino anymore.
By the way, what do you mean by voice recognition?
1. "Listen" to some voice and guess who it is?
2. Recognize the meaning of some words? (in which case it's called "speech" recognition,
not voice).
Beside this, there are many levels in speech recognition:
1. Recognize a few words (e.g "left", "right", "forwards" "backwards", etc..., to control some
kind of robot, with a unique speaker
2. The same recognition, but multi-speaker
3. Recognize the whole dictionary, unique speaker
4. Same recognition, multi-speaker.
You can understand that the constraints are quite different. The first one can be done
(parobably) with a light Cortex M3 (depends on the number of words), but for the 4th,
you need something quite powerful. I'm not sure a plain PC can do it. I have used
dictation softwares, it simply doesn't work.
Dora.