I am running:
Varia Vision SW: 3.50
RTL510 SW: 3.20
Edge 520 SW: 12.60
My RLT500 SW: 3.80 sends a vibration alert to my Varia Vision when cars are detected.
I haven't been able to get this functionality with the RTL510.
Unless there is a setting I have missed, please enable this feature in RTL SW 3.30 or higher.
This is super useful, as I sometime miss the visual clue from the Vision and beep from the head unit, especially when there is a lot of wind noise during a fast descent and I my eyes are glued to the road.