If you're referring to the sort of
voice recognition used to control your wingmen, it's actually built into the engine itself, at least for Windows builds. Most of the nightly builds and release candidates don't have it enabled, but it is in the most recent official SCP release,
3.6.10 final, and I'm assuming it will be in the final release of 3.6.12 as well. You'll need to enable the feature via a launcher flag, and like the wiki link I posted explains, you'll also have to "train" Windows' voice-recognition function in order for it to function properly. I've played with the feature turned on once or twice, and it actually works remarkably well.