There's already a couple of other options that are much closer to being on the market. The Owl:
http://www.theowl360.com/
And also the Cerevellum:
http://www.cerevellum.com/#/home
I'm pretty interested in one of these myself. I'm currently living in an area where drivers aren't accustomed to cyclists on the road. Couple that with a lot of truckers and 3' of shoulder to work with and it can get a little sketchy. Looking over my shoulder is great but always creates a little instability, plus I don't do it as often as I should. I used a helmet mirror years ago but they jiggle too dam much and you also have to change your focus to something that's 6" from your eye(which I don't like about the op's product).
The Cerevellum is the only one of the 3 that mentions image stabilization, which seems like a big factor to me. It also continually records the last 10 minutes so if you do get smacked by a car, there is evidence as to what happened.
This may be excessive nonsense to many, but increased security and awareness is good. I spend an overwhelming majority of time riding by myself and could appreciate one of these products. Occasionally I'll get an oversized load coming up behind me with no lead car. Unless you happen to look back at the right time, you don't see it until it's beside you. It would be nice if the prices were lower.
I have never tried the barplug variety but may have to.