Only for the geekiest (or most paranoid): the HindSight is composed of a small camera that attaches to the handlebar or the seat post and lets the bicycler see what’s coming behind him or her. If you wonder, the manufacturer says that the system is “unaffected” by (normal?) road vibrations.
At the moment, there is no commercial product, but it is said that “a working prototype is available upon request” on the Manufacturer’s website (Cerevellum)
Next Story: Lobster-Eye X-ray Vision