You don't generally roll your own high quality offsite voice processing and recognition. You farm it out to someone else. Apple is a bit of an exception, since they more-or-less pioneered offsite VR.
In fact Apple bought out another company to get their VR technology so it could be used in Siri and Dictate.
Nuance's
Dragon Naturally Speaking is just about the only surviving VR that actually runs on a Mac or PC and that requires a lot of "training" to get acceptably accurate translation and can cost anywhere from $150 to $999 depending on the extent of the vocabulary. (That cost includes the headset microphone needed to get the best voice quality for VR.)
