Garmin Edge 510 with a K-Edge out front mount. Meets every item on your list of wants. Works flawlessly with Mac OSX (I'm use mine with a Mac Pro and MBP both running Mavericks).

One note, I suggest you buy the Edge 510 solo, and then add their new Garmin "magnetless" cadence/speed sensors. It will cost more, but the sensors are way easier to install, and hopefully more reliable. I bought the Edge 510 Performance Bundle and then found out about the new style sensors. I get some occasional erratic cadence readings and hopefully these will solve the issue, they arrive from Amazon tomorrow. Alternatively you could buy the Performance Bundle, sell the cadence/speed sensors and keep the HRM which you will want also.