When you wake, you put the headband back onto its charging shelf on the clock. The screen comes to life, showing you a very cool graph of your night.

You can walk through it using arrow keys. The clock, and the graph, indicate where you were at each five-minute interval: awake, in light sleep, in REM sleep or in deep sleep. You can also step through screens that display your sleep-cycle tallies in huge digital numbers: “2:54 REM,” “0:35 deep” and so on.

Everything is polished and easy to use, from the way the headband snaps magnetically onto its charging shelf to the way the alarms themselves ( music or nature sounds) slowly grow louder the longer you ignore them. If you like, the alarm can try to wake you where you’re sleeping lightly, to prevent the grogginess that comes from being awakened from a deep sleep. (It will never wake you later than the time you’ve set; you specify how much earlier you’re willing to accept.)

And it’s truly amazing, if not a little creepy, to see all of this data about a part of your existence that you’ve known nothing about until now.

But as my wife said, “If I wake up and feel lousy, I don’t need a $400 gadget to tell me it’s because I didn’t sleep well.”

Ah, but that’s where the coaching comes in.

The Zeo stores your sleep records on a memory card. As often as you can, you’re supposed to pop it out and insert it into a U.S.B. card reader (also included) on your computer. At this point, you can go to MyZeo.com and upload your data to the Web.

Now the real fun begins. This Web site lets you slice, dice and cross-compare your sleep data in a million ways.

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It starts with a bar chart of your nightly sleep scores. This number (your ZQ, as the company cutely calls it) is a single convenient score that takes into account both the negatives (like disruptions) and the positives (REM and deep sleep). During the month I wore the Zeo, my average was about 70, which is typical for middle-agers like me.

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My highest was 105. That was for a luscious 10-hour sleep after an all-nighter.

But you can go much deeper with your statistics. You can plot the quality of your sleep, or one type of sleep, over time, by week or month. Or plot these characteristics against each other, looking for cause and effect. See whether your bedtime affects how long you sleep, whether you get more deep sleep on weekends, whether caffeine in the afternoon affects the number of times you wake up in the night, and so on.

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Weirdly, the Zeo system almost completely ignores exercise. There’s no way to report how much you exercised on a given day, to see if it affects your sleep. (Hint: It does. A lot.)

In any case, you get much more utility from all of this if you take the trouble to fill out the Sleep Journal online, where you’re interviewed about events of the previous night: “How sleepy were you when you went to bed?” “How much alcohol did you have within three hours of bedtime?” And so on. The analysis can take these factors into account.

The final benefit of all of this is the coaching. For six months, or longer if you’re willing to pay for it, Zeo’s busy little automated writer robots send you daily semi-personalized e-mail messages, filled with analysis and advice. “It looks like you held to a more consistent sleep schedule in this step than during your baseline,” an initial recording period, it might say. “Well done!”

So will spending $400 on the Zeo make you a better sleeper?

Well, no and yes.

First of all, the headband itself may make it harder for you to fall asleep at first; it has to be tight enough not to fall off during the night. (In my e-mail column next week, I’ll review a rival product, the SleepTracker, in the form of a watch. Sign up at nytimes.com/email .)

Here’s the part that may really bug you, though: the Zeo is soundly based on modern sleep science, and was developed with all kinds of experts. But its 7-Step Sleep Fitness Program, and all the coaching, basically boils down to a list of well-documented sleep tips that won’t come as a surprise to anyone.

You know: Don’t drink alcohol or caffeine before bed. Make your bedroom cool, dark and quiet. Don’t use your bed for anything but sleep and sex. Don’t watch TV, use the computer, do bills or fight in the hour before bed. Don’t sleep with your dog. And so on.

The real question is: if this information is so well known, why are half of us still exhausted all the time?

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Simple: we know these rules, but we don’t follow them. They’re lifestyle changes. They’re a hassle. They’re low priority.

Just watching the Zeo track your sleep cycles doesn’t do anything to help you sleep better. Plotting your statistics on the Web doesn’t help, either.

But the funny thing is, you do wind up getting better sleep — because of what I call the Personal Trainer Phenomenon. People who hire a personal trainer at the gym wind up attending more workouts than people who are just members. Why? Because after spending that much money and effort, you take the whole thing much more seriously.

In the same way, the Zeo winds up focusing you so much on sleep that you wind up making some of the lifestyle changes that you could have made on your own, but didn’t. (“Otherwise,” a little voice in your head keeps arguing, “you’ve thrown away $400.”)