FORTUNE — It’s been almost a year to the day since Jawbone released the UP, a wristband computer that tracks motion — the number of steps you take and the hours you sleep, mostly. Actually, it’s been two years since the UP was first introduced, but in 2011 many of the bands failed, and the company apologized and pulled the product.

Last week, Jawbone released an update to both the band and its smartphone application which it’s calling UP24 — as in, 24 hours a day. Before, if you wanted to see how much you were walking or sleeping, you had to plug the wristband into the headphone jack on your smartphone. The band now has bluetooth, so it can send updates to the application running on your phone. And the app can send you push notifications that might prod you throughout those 24 hours to walk a little more or get to bed a little earlier, so you reach your daily health goals, which on the UP system default to walking 10,000 steps and sleeping for eight hours every day.

Despite my general skepticism toward products that make a game out of healthy living, and my sense that the people who purchase, and whose health is improved by, a $150 wristband are the least of our health care system’s worries, I’ve been using the UP off and on for a year now, and I like it. I like how unobtrusive it is, and how little I think about the fact that this thing on my wrist is tracking my movement. I like the few interruptions it causes in my day: vibrating angrily if I’ve been sitting for too long (an hour, in my case, but that’s adjustable) and vibrating me awake in the mornings. The additional notifications, with the update, are unobtrusive too — I’ve turned off pretty much all the push notifications and during my normal weekly routine I check in with the app maybe once a day. Maybe not. It’s no big deal.

I’m a pretty bad user, but that’s fine. The UP gives me a very rough sense of two rather important data points: walking and sleeping. As a New Yorker, hitting the 10,000-steps-a-day goal is fairly easy. My commute accounts for roughly 6,000 of those steps. Add in a 20 minute walk to lunch or after work, and I’m basically there. My sleep, on the other hand, is a mess. I honestly had no idea just how bad it was until I began wearing the UP.

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I’m far from alone. Most people have no idea how much (or more accurately: how little) sleep they get. Russell Sanna, the executive director of the Division of Sleep Medicine at Harvard Medical School told me that there is just “a huge amount of illiteracy around sleep. We’re a 24 hour society now, and since your doctor didn’t learn about sleep health, you didn’t either, when you were learning about basic health.”

We don’t sleep like we used to, we have more drugs to keep us awake than ever before (and still more coming), and culturally, working after just three or four hours of rest is viewed as heroic, when really it should be viewed more like showing up to work drunk. “When you’re sleep-deprived, within 18 to 24 hours, your cognitive performance is equivalent to 0.1 alcohol in your blood — 0.08 is legally drunk,” says Sanna. Sleep, he adds, is a “gateway issue” — it affects so much of our overall health that devices like the UP are incredibly important because “they make sleep part of a conversation we’re only just starting to have.”

Having a band on your wrist that is keeping track of how well you sleep has another, not-at-all technical side benefit. It’s a reminder. My UP, and talking to Sanna, forced me to reconsider how I get ready for bed. Now I plug my phone into its charger in a different room, far enough away from my nightstand that I’m not tempted to stare into its glowing screen and disrupt my ancient circadian rhythms.

There are many things for which I don’t use the UP. I don’t share my data with any “teammates” as the app calls them. (My colleague Jessi Hempel and I were, briefly, linked as teammates but it was honestly creepy to see a graph of her sleep patterns, and to find out that she’s a much earlier riser than I, and to know that she could see the blip on my graph around 5 a.m. when I get up every morning to let the cat out, and back in, and then out again.)

The fact that I’m a haphazard user of the UP product isn’t actually bad news for Jawbone because of an important point: I’m still using it. Jeremiah Robinson, VP of software at Jawbone, sounded delighted when I told him just how casual I was with his product. “When we look across health and wellness, you see the same patterns of adherence, again and again: The first week in is best week. Over time motivation wanes. We took a long look at this,” he says. “Being healthy is so aspirational, why is health management such a chore? Why are people failing to fulfill their aspirations? Our goal was to really break that pattern of adherence. To make it hip, sure, but also to understand the science of behavior change.”

“One of the biggest things,” he continues, is the “need to capture people in the moment of intent, or intervention. I don’t believe people will use something if it doesn’t blend into their life.” I thought of that buzzing vibration — it’s happening just now, in fact, as I type this. I’ve been sitting for an hour. I’m going to get up and go for a quick walk around the office.