Like someone else has brought up already, the existing applications we've seen of Glass are all fairly obvious from years of sci-fi.
The real magic sauce is execution.
More than that, the number of people who can pull off Glass in this world, other than Google, is close to zero. Nobody has the combination of hardware expertise, UX expertise (questionable in this respect, perhaps), and sheer big-data chops.
> "Someone like Apple could probably do it if they really wanted to take on Google in this market."
I don't think so. In fact I think Google is already outrunning Apple in many ways. Look at Google Now that ships with the latest Android, predictive tasking where your phone realizes what you want without you having to go get it.
While Apple is running around with the voice-recognition toy known as Siri. Heck, I'm a loyal iOS user and I never use Siri. It's a gimmick to demo to your friends, it's not smart or wide enough for any real practical use.
See also the looming, gigantic failure of iOS6 maps - a horrifically broken data set and search tech wrapped in excellent UX.
Or, if you're an iOS dev, take a look at iCloud, whose API is still horrifically broken a year after launch and notoriously difficult to work with.
I think Apple has more than amply proven that, when it comes to big data, machine learning, and AI, they have nothing on Google.
Fun anecdote: I was standing in Manhattan today and typed in "24 Orchard" (expecting to call up the address at 24 Orchard St) on iOS6 Maps. It took me to another state. This is asinine behavior I've never experienced with Google on any platform.
IMO the only company that stands a real chance at tackling Glass is Facebook. They're the only ones with the proven big data expertise, but they are also dramatically lacking in building devices and associated software.