My OLD as Dirt Gamin ate it and in the same boat looking at using the phone.

Doing a bit of research and about to pull the trigger. I have been looking at the Wahoo set up and you can use ANT compatible devices with it and Cyclometer app.

The thing selling it to me is the Case is like a Otterbox and will give some protection in light rain and hopefully survive a crash. More importantly they sell a piggy back battery that will give you 5+ hours of run time. The basic set up with mount, Cadence speed sensor is $150 and $50 for the piggy back battery. I believe your HR monitor will plug and play but read their site to be sure.

$50 cadence/speed sensor and a $14 mount for each additional bike although you may get buy with just an app if high accuracy is not super important on speed and distance.. I have seen some discrepancy on a couple apps I have tried over what my bike computer says. Have not tried cyclemeter.

http://www.wahoofitness.com/