02/11/2012 12:44 pm ET

Tracking Sleep Cycles

Sleep ranks right up there with weight in the pantheon of health issues to obsess over: Millions of people worry that they aren't catching enough ZZZs, or that the ones they are catching aren't high-quality.

Those numbers are far too large for gadget-makers to ignore. As a result, a growing number of devices purport to track, coach and improve sleep performance, taking advantage of the computing power of mobile phones and personal computers.

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