A smart or silent alarm is supposed to prevent waking you up during deep or REM sleep. If you wake up during those restorative stages of sleep, you might feel groggy and not rested. As you can imagine, a smart alarm is only as reliable as the ability of the tracker to accurately detect the stage of sleep you're in. However, if you maintain a consistent sleep pattern, you can wake up every day at the same time without requiring an alarm clock. That's what I've been doing for the past year or so.