The best way to stay safe while biking is to stay visible to those you share the road with. And while concepts for laser-based systems that create a highly visible virtual lane around your bike have existed for years and years, they're finally real (and cheap!) now.
A Korean company called Slancio makes this rear safety light that includes a requisite set of flashing red LEDs, but also a pair of lasers that produce a thin set of lines on the road on either side of your bike. Not only do they add to your visibility at night, they also create a safe space around your bicycle that most drivers and other riders will subconsciously stay clear of. It's a brilliant idea that's made all the more amazing with a less than £15-odd price tag that makes these a no-brainer upgrade for your ride.