I'll just point out the most obvious one that is totally indisputable: about the same time Trayvon might have started the suggested process that would include calling 911, Zimmerman called the police on their non-emergency number (NEN) and got them dispatched to the location.
Let's put it this way: you're implicitly asking to know the truth of the incident; I suggest you don't ask unless you're willing to face the truth, whatever it might turn out to be.
The investigating officer testified at the trial that when he lied to Zimmerman and told him a video had been found of the entire incident, he looked relieved and said "Thank God." Assuming that someone with a documented history of fighting like Martin would want the truth to be available for the authorities is ... a bit further than I'm willing to go, and there fails your concept ... well, unless you put the pair of glasses on Zimmerman.
I'll bet you more than a few Neighborhood Watch types are going to start using Google glasses when they become generally available.
Which strongly argues for covert monitoring, the same reason a lot of people prefer concealed to open carry. At net such an overtly visible system might get more people hurt and killed....
The question is: what is the MVP?
Which brings me to my first point: passive always on is nice, unless of course you are the criminal, but expensive in battery power for which there is no Moore's law. Given that, it should take very little to get it going, which isn't necessarily compatible with the MVP of a smartphone app capturing sound.
I'm imagining something like the Cisco Flip but at 360 (or maybe 720) and with much better batteries. (My Flip uses 2 AA batteries or a rechargeable battery pack.)
I can imagine someone getting mugged, perhaps violently, for their Glass or some future version glass.
