The Garmin Varia RVR315 is a compact rearview radar for bicycles that detects vehicles approaching from behind, alerting you with visual, audible, and vibration alerts on paired Edge computers, smartphones (via the Varia app), or other compatible devices up to 140 meters (153 yards) away, significantly enhancing cycling safety and awareness. It's easy to mount on most bikes and offers up to 7-8 hours of battery life, making it a simple yet powerful tool for cyclists who want to know what's coming.