So one of the most common pieces of advice you’ll read about getting better sleep, including in sleep-tracking apps, is to stop using tech a few hours before bedtime.More on Big Tech - Microsoft: The company’s $69 billion deal for Activision Blizzard, which rests on winning the approval by 16 governments, has become a test for whether tech giants can buy companies amid a backlash.Dr. Michael Miyamoto, a medical director for Amazon, said the company had done internal studies comparing the results of its algorithms with data measured with polysomnography, the gold standard of sleep tracking that involves hooking up sensors to someone’s face and neck to measure eye movements and brain activity.Dr. Miyamoto said that Amazon found the Halo Rise results to be accurate, but that the company had yet to work with a third party to validate the accuracy of the product, though it plans to.Olivia Walch, a mathematician who has studied circadian rhythms, said that because research had shown that sleep-tracking wearables had trouble distinguishing sleep from wakefulness, it would probably be even harder for motion sensors to do the job."