> it's borderline useless for rear-view mirrors, which do not shine a light back at the cyclist.
Not sure I understand what you're getting at here. Retroreflective strips reflect light back from the source to the viewer. In the case of a rear-view mirror, the light source is the tail light of the vehicle, which will hit the retroreflective material, reflect that back towards the vehicle where it will be seen by the driver in their rear-view mirror.
Not sure I understand what you're getting at here. Retroreflective strips reflect light back from the source to the viewer. In the case of a rear-view mirror, the light source is the tail light of the vehicle, which will hit the retroreflective material, reflect that back towards the vehicle where it will be seen by the driver in their rear-view mirror.