Safety on the road has always been a concern. As a result I often am twisting my neck to see if there are cars behind. This is especially true when I ride 2 abreast with a friend (I choose to change to single file if I know a car is behind). Yes I have tried every mirror option available (helmet, bike handlebars, etc...) none of them consistently gave me the confidence that I knew what was behind me.
But the Vario does what it says. An audible as well as visual warning, well before I can hear a car coming. It was 100% accurate-I was quite impressed. What happens when 1 car passes you? Well, the noise of the 1st car makes it impossible to be certain if there is another car or now, so you have to turn your neck, which invariably means you sway a bit (even if just a little) in your lane. The Vario addresses this too. The red warning lights stay on if there is a 2nd or 3rd car until all cars have passed-genius.
I am a Wahoo user and it paired just fine with my Elemnt Bolt, full functionality.
Why almost perfect? One of my concerns is the poor driver who may drift out of their lane and hit me (much more of a problem with Cell Phones). My preference would be to have a camera that would show me that a car was getting dangerously close so I could head to the ditch and have some control of the outcome. Radar can't do that. So it is not all I could want but it is a massive improvement.
Had I realized how well it works I would have bought it sooner. Game changer!