But why are you in the market for a sleep tracker? Sleep tracking is a little bit bogus. I’m a terrible sleeper, but neither the Sense nor any other sleep tracker has revealed anything particularly helpful about what was happening to me between the sheets. If you’re not sleeping well, you almost certainly know it already, and there’s a good chance you know why. At best, the tracker adds a layer of empirical precision to a situation already evident in your midafternoon yawns.

What do you do with its data? There are many potential reasons for your poor sleep — you’re working too hard, you’re partying too hard, you’re too stressed, you have insomnia, you have a baby, your neighbors are noisy, you suffer some physiological problem — but the sleep tracker isn’t going to be able to fix any of those. As I studied the Sense’s readings every morning over the past week, I was puzzled over what to do next. I knew I had slept poorly; I had gone to bed too late, woke up too early, and I felt terrible. Why did I need a device to prove that? And unless the sleep tracker was offering to take care of my children for me, why should I bother with its data?

The Sense comes in two parts that work more or less automatically. There’s a tennis-ball-size orb that sits on your bedside table. It remains plugged into the wall, wirelessly connects to the Internet, and it packs an array of sensors. The orb can measure the brightness of the lights in your room, temperature, humidity and the concentration of particulates in the air, and it can also record sound in certain cases, like snoring.

The other part of Sense is the Sleep Pill, a tiny, battery-powered device that attaches to your pillow and detects the movement of your body throughout the night. You can use two Sleep Pills with each Sense orb, letting you track your sleep and your partner’s. The Sleep Pill’s battery lasts about a year, according to James Proud, the founder of Hello, the company that makes Sense. The Pill uses a hearing-aid battery that can be bought at just about any drugstore. The Sense orb, which goes on sale this week, comes in black or white, and sells for $129 with one included Sleep Pill. An extra Pill costs $39.

The Sense also has a well-designed app that works on newer iOS or Android devices. The app keeps a diary of your sleep and reports a daily score on how well you slept. The app also lets you set a “smart alarm,” which wakes you up when you’re in the phase of your sleep cycle most conducive to waking up, usually a few minutes before the time you set. This way of waking is supposed to make you feel refreshed, though not by much; if you haven’t slept enough, you’re not going to want to wake up even if the alarm is smart.