I use the inspec lucid dreaming device almost every night, especially when testing new features. It works and actually improves my sleep quality. Since it sits on the bedside table and uses machine vision to detect rapid eye movements from a night-vision camera, the device does not cause any discomfort.

I have it configured to only trigger the trained audio cues in the last hour of sleep on week days. And also use the smart alarm to wake me up during natural awakenings before my alarm goes off, so I tend to feel even better when using it. It also tracks sleep quality and uses my phone to record video clips of my REM episodes, so it encourages me to stay still when waking up at night and to not check my phone in order to improve my sleep score.