A bunch of companies are selling laser lane markers (perhaps rebranding a gadget being pumped out of a factory somewhere on the outskirts of Shenzhen). These are rear lights for bicycles that incorporate downward-sloping red lasers that create lines on the road behind the bike.
This is for some reason expected to be safer than a blinking red light on its own.
These are available online for $25 or less. I’ve never seen one in the wild.