Invention Daily #15

A flying drone that tails a cyclist at about 5 meters up, with front and rear facing video cameras.

Included are (1) a couple of video-processing algorithms that calculate real-time motor vehicle trajectories, and (2) a warning buzzer for imminent cyclist death.

This would give cyclists time enough to pray, or to randomly duck left (or right if you are in the other Coriolis sphere of affluence).