Key Features: Varia RVR515 is a smartphone compatible cycling radar and provides awareness of vehicles approaching from behind up to 140 metres 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,Compact vertical design mounts easily to most road-use bicyclesBattery life: up to 7 hours   .