The Garmin RearVue 820 is Garmin’s new cycling radar rear light for 2026, aimed at anyone wanting earlier awareness of approaching traffic. StVZO approval, radar range up to 170 metres, real-time vehicle alerts and long battery life make it one of the most interesting safety upgrades for road, gravel and everyday bikes. In this Garmin RearVue 820 review, we examine radar reliability, everyday rear light performance and whether its price is justified against the Garmin Varia RTL 516, RCT 716 or Sigma RECO 80 LINK.