GPS maker Garmin has a new line of bike accessories that could help bicyclists stay safe at night and on busy roads. The "Varia rearview bike radar" combines a flashing taillight with a sensor that detects the distance of trailing traffic. A separate display on the handlebars shows the position of multiple vehicles up to 300 feet away, and the light itself increases in intensity as traffic draws near or when braking. (Get a second one and there's even a turn signal function.)
The Varia smart bike light coordinates with a GPS unit, tracking your speed and tilting the light up more as speed increases, though not so much that it'll blind oncoming drivers and other cyclists. Six-hundred lumens should be plenty unless you need serious bad-weather visibility. The 2.5-hour battery life leaves something to be desired, though.
These high-tech accessories aren't cheap, either: The radar and taillight package will set you back $375, and the headlight is $200. Perhaps something for the deep-pocketed cycle hound, but others may have to settle for looking over their shoulder once in a while and adjusting their headlight manually.