The author is using sleep cycle on his phone, which is not a good method of tracking sleep cycles. He says "their ability to wake me in “non-deep” sleep pretty spot on" - you're not in deep sleep in the morning anyway, or very unlikely. So any "app" has a good chance of waking you from REM or N1/2.
We've been building a headband which monitors your sleep state, and uses sound to improve your sleep performance. Literally, improving the neurological function of your brain while you sleep.
I used one of our early prototypes to win the Sleep World Championships (https://soundmind.co/blog/neurohacking-the-world-sleep-champ...).
We're currently working on improving the fit and comfort before finalizing industrial design. You can find out more, and join the waitlist at https://soundmind.co