Who wants to be a sweaty mess after biking to work? “No one,” is the answer FlyKly is banking on. The start-up has created an electrified rear wheel that can retrofit onto almost any bike. Pedaling becomes effortless, and co-workers will thank you.
The 250-watt motor  propels the bike up to 20 mph. Electricity passes into two rings of magnets  inside the housing. The current turns the magnets, which drives the wheel.
A round circuit board  at the center of the housing relays commands to the motor. GPS tracks the bike’s location, mileage, and routes; Bluetooth links the system to an app.
The 36-volt battery  charges in several ways. When the bike coasts, the wheel spins the magnets, which generates current. A socket charges the cells within three hours.
When a rider locks the wheel, current to the motor stops flowing. Without power, the two rings of magnets hold each other in place and prevent the wheel from turning.
Riders control and monitor the system through a smartphone app, which records trip data and monitors the performance of the motor and electronics to help detect issues.
FlyKly Smart Wheel
Top speed: 20 mph
Weight: 9 pounds
_This article originally appeared in the February 2014 issue of _Popular Science.