Garmin Varia RTL515, Cycling Rearview Radar with Tail Light, Visual and Audible Alerts for Vehicles Up to 153 Yards Away - 010-02376-00

Rearview radar with tail light provides awareness of vehicles approaching from behind up to 153 yards (140 meters) away
Pairs seamlessly with your Edge bike computer and compatible smartphone as well as select Garmin wearables or the radar display unit
When used with your compatible smartphone, the Varia app provides graphics — plus tone and vibration alerts — that indicate approaching cars
When used with a compatible smartphone, Varia radar integrates with third-party apps such as Ride with GPS to overlay your maps with rearview radar alerts
Daylight visibility up to 1 mile alerts motorists to your presence as soon as possible
Compact vertical design mounts easily to most road-use bicycles
Peloton mode provides a low-intensity light flash that is perfect for cycling in groups
Battery life: up to 16 hours in day flash mode, up to 6 hours in solid mode