I don't get how this works. The only dangerous situations that you can't prevent right now are a car coming from around a blind corner or a car that wants to turn while you go straight. In the former case you'd need to look around the corner, something I can't imagine how it would do. In the latter case it would need to magically know when a car, which might or might not have been close to you for the last mile, suddenly decides to turn, and far enough in advance that you can react to it. That too seems impossible without something to detect a turning light.
Maybe I'm missing something by watching the video without sound (I'd wake people up if I did), but it just doesn't seem possible to me to help in any way. Detecting that there is a car behind me at all is something we commonly do with a utility called "ears".
This isn't for city riding. It is for riding on country roads. If you've ever done any road cycling outside of city centres, it can get very risky as the cars are going so much faster and there isn't the same road shoulder. Your ears are not enough. Personally I hate cycling on country roads because of this so I would definitely use this radar.
I agree with an earlier comment about non-visual feedback. An audio queue would be good (thinking like the trackers in the Aliens movies)
Most of the country roads I cycle along (even the ones shown in the video) have enough curves that by the time this device detects a car you would be able to hear it.
Even then I'm not really sure what the point of this device is. If a car comes speeding up behind you what you are supposed to do? Pull over and stop? Drive on the edge and get covered in mud?
Most of my riding is this, and I think the risk here is perceived risk, not actual. Generally getting smooshed from behind is a low-likelihood event. When it does happen it's on fast trunk roads (pretty nasty to ride, but also usually avoidable).
This looks like another techy boondoggle to reassure people. Cycling is littered with 'em.
I have been in a number of driver at fault cycling collisions. Although I was never hit from behind I have had 3 near misses by cars going over 40 mph. It isn't a low likelihood event.
I looked at the deaths for one year in London and 9 out of 10 where cased by undertaking HGV (heavy goods vehicles) turning left - this wont help in that case.
Though it could be useful for touring cyclists - but they often have a review mirror.
Maybe I'm missing something by watching the video without sound (I'd wake people up if I did), but it just doesn't seem possible to me to help in any way. Detecting that there is a car behind me at all is something we commonly do with a utility called "ears".