GARMIN Dakota 20 EDGE 305 310XT 705 FORERUNNER 50 305 405 Colorado Oregon 300 400c 400i 400t GSC 10 Speed/Cadence Sensor
Great--measures my RPM so I know I pedaling smoothly and not slacking!  Makes me a better rider.  Its just another add on to my Garmin 705 that increases accuracy in readings.  I also use the heart rate monitor too.