Garmin Varia RVR315 Bike Rearview Radar - Visual & Audible Alerts for Vehicles Up to 153 Yards - Cycling Safety Device for Road & Mountain Bikes - Perfect for Commuting & Group Rides

The Varia model tested was the RVR315 without the taillight (with the light it’s model RTL515).First of all, it’s a solid Garmin product. It is supplied with 3 seat post profile inserts and two sizes of O-rings to fasten the unit to the bike seat post. A micro USB cord is supplied for connection to a power source (not supplied). The charging port is protected by a well -designed cover but care should be taken when inserting the USB plug. As with all USB sockets, the unit can be damaged if the plug is inserted incorrectly or with excessive force. Battery life seems to be 3-4 hours. Battery is also reported on the Varia App screen. The RVR315 was tested with an iPhone 7 using the Garmin Varia App and the RidewithGPS App. The unit easily paired with both apps and will alert you if pairing fails during a ride.The radar will detect multiple cars behind you at up to153 yards as claimed. The unit does not report “all clear” unit the last car detected has passed you (great when you can’t see them all). However when you turn onto a side street and a car turns with you, the detection may be mixed. When riding straight and a car turns out of a side street behind you, the Varia takes a moment to detect the vehicle and it may not be detected until it is right on top of you. Overall the performance is quite impressive, it picks up vehicles at a distance and will alert you well before you can hear a vehicle approaching.VARIA AppThe app is streamlined with options to select some sounds/vibrations on the interface. The app displays a high contrast track on the phone that is readable even in bright daylight. Be aware the app does not sleep so the screen is using more battery time. Audio signal volume is moderate but adequate.RIDEwithGPS AppAfter pairing with the app, RwGPS adds a graphic track to the left/right side of the screen (your choice). It displays well, but the track is not displayed as well as the VARIA app. Also the RwGPS screen may enter sleep mode if selected and you lose the visual display, but the audible alerts will still be heard.Bluetooth Audio with Both AppsIt is possible to pair an external Bluetooth speaker with the app/phone to increase the audible announcements, but the results may be mixed with the external Bluetooth unit. An older Bluetooth 3.0 speaker did not report all of the expected tones all of time. Some alerts remain silent even as the phone app showed an approaching vehicle. When a Bluetooth 5.0 speaker was paired, the unit reported the audible alerts consistently. One curious note is that depending on the app or the external speaker the audible alerts may be slightly different tones.City riding with the Varia may yield some spurious results but it still quite good. Out on the longer stretches it is very consistent. In both scenarios it adds a safety factor that is hard to beat for any serious cyclist.