PeteHski

A camera based system could potentially do that. They can certainly detect different vehicle types, which could be useful.

PromptCritical 

Update on my Varia radar (from my perspective) after a few rides in San Diego and week long tour of Bryce, Zion and Grand Canyons.

1. As we already knew, there is no side to side sensing capability.
2. The unit last ~5-6 hours, depending on the amount of traffic.
3. In heavily trafficked areas, it is an annoying nuisance.
4. It is very helpful in low traffic areas and for overtaking traffic that may be changing lanes to the right for an intersection, freeway onramp, etc.
5. It is very sensitive, occasionally picking up another bicycle and doesn't miss motorcycles.
6. If using the Varia app, it does highlight a warning if the traffic is approaching at a high rate of speed (I don't know what speed triggers that).
7. The bluetooth connection drops out about once per hour on my road bike (single) but never did on our tandem ride of the canyons last week.
8. When the bluetooth connection drops out, there is no audible warning.
9. The bluetooth connection will reestablish itself on my Wahoo Bolt bike computer, but not on the Varia app.
10. Siri does not link to it, which would be helpful for turning the audible alerts on and off depending on location.

Hope that helps.

Polaris OBark

I suspect the ~5-6 hours is either due to the bluetooth connection, or you have it on steady rather than flash, or both.