Bests & Worsts Reviews from Amazon

While the GSC10 sensor is a combined wireless Speed/Cadence sensor, these devices are self-contained units. Pros: 1. No magnets. These sensors use inertial sensors to determine when a "tick" has occured. That means fewer moving parts. Effectively the cadence sensor just attaches to your crank, and the speed sensor attaches to the spindle of either of your wheels. ANT+ technology means no wires on your bike, similar to the GSC10, but in this case there are no parts that are externally exposed and easily damaged. 2. No penetrations means they are more waterproof. These are actually rated water resistant to 10m (1 ATM), eliminating a common complaint of the GSC10. 3. You can choose only the sensor you want. The speed sensor, unless you desperately need your real-time speed updated 3 times a second, is highly optional. The speed sensor still needs a GPS signal to calibrate. Cons: 1. You now have two batteries to replace, instead of one, unless you only use the cadence sensor. 2. They are more expensive. than the GSC10. 3. The speed sensor will ONLY attach to wheels with a spoked hub. That means no tri-spoke carbon wheels, Aerospokes, disks or similar wheels. It would probably work on a hub-based power sensor but using the front wheel in that case would probably be a better option.