Right now, it’s all manual with the rider picking the right gear, but in the near future a Bluetooth-enabled system could cut the cables and rely on your smartphone to automatically change the gear to a perfect one.
"We've cut the cables between the switches and the gears and replaced them with a smart, low energy version of Bluetooth designed for very long battery life," Cambridge Consultants Limited‘s Tim Fowler explained.
Of course, some tuning on part of the rider is required initially. "In set up mode you pedal for a while and then set the maximum and minimum cadence levels either side of where you feel comfortable," Wilson said.
From there on, the smartphone gets readings from sensors on the front determining the speed at which you are riding and a sensor near the pedals that tells the pedalling speed (that is the cadence). Using those two values, it’s not hard to compute the right gear, and the switch then happens automatically.
With the next logical step being location awareness via GPS, the gears could automatically change ahead of a hill you have to climb or a downhill section. Shimano is mentioned as one of the first possible partners, and hopefully we will see the new system in bikes soon.
source: New Scientist