In the past I’ve wondered whether it’s possible to use a single Garmin Forerunner 305 GPS trainer watch with two Garmin GSC 10 cadence sensors (i.e. with two different bicycles). The answer is, yes, you can; however, the device can only work with one sensor at a time. When you switch from one bike to the other, you have to enter Settings -> General -> Accessories -> Cadence Sensor, and from there perform a rescan, so that the 305 will pair with the other cadence sensor. So, you can only be paired with one sensor at a time.