> I'm struggling to understand the need. I ride my bike every day but I don't remember the last time I was surprised by a car approaching from behind.

Not get rear-ended by a car? There's also model with a camera to collect evidence. I have the one without the camera, just the radar and a light.

> Where in the world do you live / where do you typically ride your bike? In what situations are you glad to have that radar?

Central and Eastern Europe. Whenever I share the roads with cars. Although I'm more relaxed on outdoor paths or gravel roads where I don't have to keep an eye on cars all the time.

For MTB you probably don't need it, but in road scenarios it's great.