"Consumption" != "entertainment".
A navigation system is made for consuming content, too.
You could say the same thing of a craft knife: it's not a surgical tool. Sure, in a very particular set of circumstances, a surgeon will use one, but that's 'blah blah'. It's not the way the items is used by the vast bulk of its users.
If you compare a GPS unit the user has to turn their head or worse look down to use vs. a Glass sitting above their vision with the directions always available at a glance, the Glass is pretty clearly superior. Realistically, many users use their phones for GPS and don't have a proper mount whereas Glass will always be properly mounted to be hands free, so it's probably even safer than the most common thing of just using your phone for directions.
Aircraft are not cars - watching for other aircraft is typically handled by air traffic controllers for most aircraft that will have HUDs, or the HUDs are capable of displaying the locations of other aircraft.
Google Glass interfaces are not designed to be HUDs to be used when driving, and there is no ATC or automatic detection of other vehicles when you're in a car.
The two use cases are quite different.
My flight instructor phrased it this way. In a car in good conditions, you spend 95% of your time watching your surroundings. In an aircraft in visual conditions, you spend 70% of your time looking outside the cockpit. In an aircraft in instrument conditions, you spend maybe 5% of your time looking outside.
The pilot is focused on the hud first, the outside environment second. A car should be completely reversed from that.
My GPS (actually my phone in a special car dock) is right up on my dash/windscreen, always in my peripheral. I glance at it with ease. And while I am glancing at it, the road ahead of me is in my peripheral. That sounds a lot like what people are describing how to use Glass for GPS. Where are you mounting your GPS that it takes more than a glance to see?
Correction: Military heads up displays have already been proven by the military to be much safer. In order for their results to apply to Google Glass, they would have to install Angry Birds, Facebook, and YouTube on those devices, too.
I remember from that testing that there were three ways the threat was categorised by distance: safe, lethal, very lethal - the middle one was very specifically not "kinda in danger" :)
Do cars integrate with Glass like this?
Satnav systems potentially make us worse drivers as well. If I have to look down at the system (which I do) it's much more intrusive than Glass, which only requires I look up and slightly to the right to see. It is certainly not directly in front of your eye unless you are wearing it completely incorrectly.
Have you had Glass on? It isn't as intrusive as you appear to believe.
https://news.ycombinator.com/item?id=6640895
Two people who have tried.
Unrelated: Looks like another topic nuked: http://hnrankings.info/6640532/
It sits above my field of vision and is no more distracting that the frames of my glasses.
When Glass is in nav mode, that's all it does. Shows you the next turn and/or the route overview.
Glass could potentially make us worse drivers too. Satnav systems have guidelines issued for usage. Here, we are dealing with illumination directly 2 inch in front of my eye. I will go by your data, but would rather want California DMV to test it out comprehensively.