"my wife" is Almost Certainly* explicitly flagged in his address book, either as an alias or through a "relationship" field. he didn't show you that part. (the same is likely true of the geofence, though a location-aware algorithm could probably do a better job inferring where your work is than who your wife is.)
I have no problem with that. This a great demonstration of what Apple does best - optimizing products to fit the needs of most users. Google already has the voice tech in place, but often fails to follow through on the usability front. A perennially annoying example for me is when I'm on the road somewhere, bring up Maps, and ask for directions from wherever-I-am to 'home'; it doesn't know where 'home' is. This is even more annoying, because there is a 'home' tag in Maps, but it doesn't get searched on. Likewise, there's no easy way to tell it that one person is my wife, another person is my business partner, a third person is my nemesis and so on.
Apple are leveraging a culture of paying attention to detail to overcome technical handicaps, but it's hard to quantify or A/B test that, and most firms aren't comfortable with a budget line item called 'magic.'
To add to the frustration, Google knows where "home" is for me, even without me telling - Latitude inferred it. Can't ask Google Mobile Maps for directions to home, though.
yeah. I'm just saying that the magic in the system is that it's a well-designed system with attention to detail, not that it's capable of leveraging anything approaching human intuition.
And when you leave the work radius at lunchtime with the cute coworker you're flirting with, you suddenly hear your wife over the in-vehicle bluetooth handsfree.
I wonder how many conditionals you can string together. "Remind me to call my wife before I leave work" is great, but "remind me to call my wife before I leave work at the end of the day, unless she calls me first" would be awesome.
In reality none of this stuff is even remotely useful, because I can't even begin to guess whether or not a given command will be interpreted properly. Natural language is hard, and reminders need to be 100% reliable.
According to the video, he said that Siri knew his wife's name from "a previous conversation". Which seems to indicate that Siri has some learning capability built in.
* a term of art meaning "certainly"