But without an accurate measure of how hard they're working, it's been a limited workout tool. Chatter on a Nike+ discussion forum is indicating that a heart rate monitor is about to be added to the package.
Using a heart rate monitor is a great way to measure fitness, focus training, more accurately track calories burned, and make sure you're working out efficiently. The launch date is rumored to be June 1, but no word on pricing or compatibility with the iPhone. If it is, combining this with the GPS capabilities of the iPhone will make this a powerful training tool.
Via I4U News