Garmin GSC 10 Speed/Cadence Bike Sensor : Works well with my MTB

The GSC 10 uses two magnets to pick-up the speed (magnet on rear-wheel spoke) and cadence (magnet on the inside of the left crank). The installation is pretty straight forward, although, the illustrations in the directions were not the most useful.

The system has worked well so far. I have not been over the worst 'bumpy' areas yet on my MTB but have been through some rough terrain and nothing came loose.

The FR-305 is supposed to use the speed from the GSC 10 when it cannot get a lock on the GPS satellites. When MTB'ing, which many times involves making many small turns, the GPS mileage reading tends to be a little short. Thus it would be ideal of Garmin could somehow combine the readings from the GPS & GSC 10 to get a more accurate reading.