Zeo Personal Sleep Coach
kk.org/cooltools/archives/5851
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
What you need is data. That's what Zeo provides. It's a clock-radio-sized device that sits on your bedside table, with a comfortable wireless headband that you wear while you sleep. The headband measures electrical signals from your brain and can distinguish between four states: awake, light sleep, REM sleep and deep sleep. The base station records all this, and displays all the data in easy to understand charts, as well as recording it on a SD card that you can plug into a computer to upload to a very good website for tracking and analysis. (It's also a great alarm clock, which can wake you at the time when you're most ready to wake, which may be some minutes before the set time)