Head- and tail lights definitely help make bicycles visible from the front and back, but what about from the sides? The handlebar-plug-replacing SideLights are designed to address that shortcoming, plus they serve as headlights, tail lights and turn indicators.
These look cool. I purchased the Cycl Winglights some years ago and thought they’re pretty slick.
https://cycl.bike/collections/winglights/products/winglights360-mag
To people pointing out how not-bright these ones are, the Winglights are apparently only 48 lumens and I never thought that wasn’t bright enough. The point was to add some visibility to automobile drivers at night, not to blind them.