Android's combined with Android Auto (in a car that supports it, or now with your phone if you have it mounted) is pretty good. No, it can't parse human language at all. It's like playing King's Quest by voice. There's a dictionary of set commands and some variation in syntax allowed. It's not without its bugs, but it's really useful in the car. One physical touch to play a voicemail/text/hangouts/facebook message, and you can reply by voice, including punctuation (if you want), and verify before sending. Navigating, finding a stop along a route, are nearly hands-free - but often still require a single touch to verify the correct choice on the screen.
The tech you want is barely available in something like Watson, but it's here. It's just a matter of cost to give it to the consumer for a reasonable price. What we have now is finally useful, at least.