Cheapest most reliable wireless cadence display?

dubcat Posts: 741
edited August 2012 in Road buying advice
Hi, I have a Garmin Forerunner watch. It is designed for running so it does not show cadence but it does record my heart rate, distance travelled and speed. All I really want from a bike computer is a cadence display so that I can learn to ride efficiently. Speed on the bike computer would be a nice to have but not 100% necessary. I want something wireless so it can be installed neatly and I would like something that is reliable. What do you guys recommend?
2010 Specialized Rockhopper
2012 Bianchi Infinito