[romanv]

It looks like it really works:

 

[Zach]

Honestly seemed a bit overreactive...

 

[Colin Lambert]

You can adjust the distance in the settings.
I have mine set on furthest for obvious reasons.
Mine has beeped at me once or twice, sometimes when I am passing a a parked car.
Who is going to be the first guinea pig who sees if it does actually brake in time! NOT ME!