When you're cycling fast at night, it's good to have a bright headlight so you can see what's on the road ahead. Once you slow down, though, you really just need a more energy-efficient low-output light that allows you to be seen by drivers. Binoreal's Radius F1 automatically transitions between the two extremes, based on how fast you're riding.
While there are already some other accelerometer-equipped bike headlights that shine brighter when the bike goes faster, they typically switch abruptly between output modes. By contrast, the F1 adjusts its brightness incrementally, starting at 200 lumens and then smoothly working its way up to either 450 or 650, depending on which of two models is being used.
It additionally alerts motorists by going to a flashing mode when the brakes are applied, and going to a pulsing mode when its gyroscope determines that the bike is turning. If the bike remains inactive for three minutes, the F1 goes into standby mode, and it shuts off completely once the bike hasn't moved for an hour.
One charge of the lithium-ion battery should be good for two hours of use at maximum brightness. Additionally, a handlebar-mounted Bluetooth remote lets users manually select output modes, in the event that they don't want to just go auto.
When not in use, the light can be removed from its mount within seconds. It's also water-resistant, so it can stand up to being rained on.
If you're interested in getting one, the Radius F1 is currently the subject of an Indiegogo campaign. A pledge of US$40 will get you the 450-lumen model, while $50 is required for the 650-lumen version – the planned retail prices are $80 and $100, respectively. If all goes according to plans, shipping is estimated to take place next April.
Potential buyers might also want to check out Garmin's Varia system. It includes a headlight that broadens or focuses its beam based on speed, along with a tail light that doubles as a brake light.
Source: Indiegogo
And, they don't need batteries, either...