I use a MAVIC Wintech... wireless with wireless cadence.

It comes with a wheel skewer that you replace your current front skewer with, a wheel magnet to talk to said skewer and the cadence transmitter and pedal mount magnet to complete the package. About $150 depending on where you buy it.

I love it. It is mounted to the left of my stem, my heart monitor to the right of the stem... I experience no interference btwn the two.

spazz