[thebruce87m]

They don’t suck. The Garmin one is also a rear light. It integrates with the bike computer to show detections.

When a car approaches from behind you get a visualisation on the bike computer showing you how far away the car is and an audio alert. If the car is approaching fast you get a different audio alert and the light flashes differently to warn the approaching car. It also detects up to three cars.

There might be improvements to be had but the implementation is pretty solid.

[ivape]

Ah. The Garmin Varia looks like it’s $200-300. Would be hard to go up against a brand like that, but wonder if you could compete on cost. The margins look great.

[debian3]

There is tons of cheaper alternatives now. Some chinese brand. The implementation is particularly hard to get right (how to avoid object that enters the radar field of view like passing next to a fence among other tricky scenario like a car that follow at the same speed as you but suddenly accelerate to pass you, etc). A lot of competiting radars will have false positives or negatives. That’s why Garmin is still the favorite product on the market. Wahoo just released one as well, and the reviews are quite positive so far. Bryton makes one, Magene, Giant, Trek, igpsport, etc.

[MezzoDelCammin]

Not even that. I think I had mine for under 150 (on some sale). Also, there are a few cheaper alternatives, but some tests have shown them to be less reliable (either false positives, or worse - false "all clear").

There's one feature they all miss. They only measure relative velocity to You. That's definitely better than nothing, but in my experience the most dangerous drivers aren't necessarily the fastest ones, but those who pass too closely. So, something like "angle of approach" measurement would be a feature I'd personally be willing to switch my Varia for something else.

[Rebelgecko]

There's some cheaper knockoffs but they tend to struggle with false positives, poor integration with our device, or weird noncompliant USB ports. (Most versions of the Garmin are still micro-usb so they're not perfect either)