I've been learning how everyone has their own 90 minute sleep cycle and when they discover what it is, they will know when to go to bed and when to set their alarm to get up so that they get the most rejuvenating sleep and wake up alert instead of groggy (which they will feel groggy if they set the alarm for the wrong part of their sleep cycle.)

This is a sine wave tracking, not a linear tracking.

Since most people struggle with sleep, this could be a powerful tool for everyone, since they will slip into sleep in a 90 minute cycle and if they try to go to sleep outside that cycle they may lie awake just getting frustrated, not knowing that they are trying at the wrong time.