The Remora fish latches onto larger fish to gain a free ride. The chosen host gains nothing from the relationship, yet looses little. It is a proven relationship that exist in nature, lets give it a try.
Presently, cars own the road, but imagine a future where the law and respect falls onto the pedestrian or cyclist. In this world it would be completely typical to see a cyclist 'latch on to a car for a quick break. Because of the car's impact on the environment, it will be in debt to the common cyclist, and will happily take on a couple 'remoras'.
This relationship will primarily be seen in town on the smaller, slower roads. A cyclist may jump from one car to another depending on their intended route. They don't expect to get everywhere by this means, but will happily take the free ride up that dreaded hill or after a long day at work.
Bike Remora uses a silicone coated magnet to secure itself to the automobile. Safety is of course a concern. The important feature of the Bike Remora is the safety leash. The leash wraps around the wrist of the cyclist and when pulled upon, the magnet recesses into the shell of the Bike Remora's body, thus becoming unattached to any surface. Therefore, when the cyclist simply pulls away from the vehicle, they are no longer 'latched'.