I've used quite a few heart rate monitoring watches in my day. I've played with Suuntos and Nikes aplenty, with whosits and whatsits galore. But the RCX5 is different in its utter simplicity. Designed to be worn while swimming, running, or biking, all of the smarts are actually in the optional sensors, leaving the watch itself as basic as a $20 Timex with a few tricks up its sleeve. The base kit - that is, the watch, heart rate band, and a battery - costs $349. Although the watch and sensors are ostensibly OS X and Windows compatible, you're going to be more comfortable using the software on Windows. I had some issues with the Mac sync and it wouldn't work at all for me using a MacBook Air. It did work on my Mac Pro at home.
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