It's called the Lucnt (pronounced "lucent") and what is it? It's an accelerometer-equipped bike tail light that's made from a single block of aircraft-grade aluminum, and it does more than you might expect.
Designed by San Francisco-based Mema Engineering, the Lucnt automatically powers up when it's slotted onto its magnetic mounting bracket, and powers down when it's taken off. It also shuts down if the bike remains immobile for over 90 seconds, and comes again once the bike gets moving.
When the bike is moving, though, the light can be set to either shine steadily at 10 percent brightness (by flipping it up), or to blink at 100 percent (by flipping it down). The blinking pattern changes with the cyclist's speed, and it goes steady when they apply the brakes – if they've already got it in steady mode, it goes up to 100 percent brightness when the brakes are applied.
It's also waterproof, and can reportedly operate for up to 20 hours on one 1-hour charge of its integrated battery.
Mema Engineering is currently raising production funds on Kickstarter, where a pledge of US$85 will get you a light – if everything works out, that is. The planned retail price is $120.
It can be seen in use, in the video below.
Sources: Lucnt, Kickstarter