VR should be pretty easy... Computers have had decent voice recog. for a while now. Japanese Navi-systems for years have also had pretty solid voice recog.
I think what you guys are referring to is dictation which is a whole other bag of chips...
It takes a fair chunk of processing power but it certainly isn't anything way out there anymore either.
IBM's ViaVoice worked pretty damn well with dictation for years now. When I tried it, it somehow managed to accurately interpret even my Slavic english accent, and that was way back in 1997.