💸Are Wearables Worth it?

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Every product has a stated job and a paid job. Ideally they point in the same direction. When the two jobs diverge, the customer is often the last person to notice.

The health wearable is a case where they have quietly come apart, and most of the people wearing one have not registered it.

The stated job is measurement. You put a sensor on your wrist or your finger, it reads your physiology, and it tells you the truth about your body. That is what the box promises and it is why anyone buys.

The paid job is different. The paid job is to produce a number that is interesting enough to check tomorrow morning, and the morning after that, for as long as your card stays on file. Whoop charges $199 to $359 a year. Oura charges a subscription on top of a $349 ring. Google now sells the Fitbit Air at $99 with a $9.99 monthly tier for the AI coaching. Every one of these businesses is valued on how many mornings you keep opening the app.

The tell

Dan Go, a fitness influencer with a large audience and no sponsor in this fight, wore an Apple Watch, an Oura ring, a Whoop, and a Fitbit Air simultaneously for a week. He bought all four himself and turned down a free unit from Whoop so the results would not be tainted. 

Total sleep time came in within about 30 minutes across all four. After that, the results started to differ quite a lot. On deep sleep, two devices put him around 47 minutes a night and two put him at 70 and 81. That is a 76% spread on the single number the category has trained an entire generation to fixate on. REM inverted the ranking: the device stingiest on deep sleep was the most generous on REM.

The Wall Street Journal ran a version of the same test through a Stanford sleep lab. Apple's sleep staging came closest to lab truth, which points toward the higher readings being the flattering ones rather than the correct ones.

We want to be careful here, because the easy argument is that the subscription companies inflate your numbers to make you feel good. We cannot prove that and neither can anyone else, which is precisely the problem. The generous pair in Go's test was Whoop, which is subscription-only, and Fitbit Air, which is not. There is no clean conspiracy to expose.

The metric that cannot be wrong

Deep sleep at least has a ground truth. A sleep lab can wire your head and settle the argument.

Now consider the products these companies actually lead with. Recovery. Readiness. Strain. These are proprietary composite scores. There is no polysomnograph for readiness. The score is not a measurement of anything that exists outside the company that sells it.

That is not a flaw in the product. From a business standpoint it is the best feature in the product. An unfalsifiable metric cannot be shown to be wrong, cannot be beaten in a head to head comparison, cannot be reproduced by a competitor, and cannot lose a lawsuit.

Go, who has 20 years of coaching behind him, does not act on wrist or finger HRV at all. He says it is not accurate enough to drive a decision unless the reading is extreme. The flagship metric of the category is the thing an informed user deliberately ignores.

Ask why the number is daily

Your physiology does not resolve meaningfully at a daily resolution on a wrist sensor. Sleep debt accumulates over weeks. Training adaptation runs over months. Trend is where the signal lives, and every serious person in this space, including Go, will tell you so. Daily is not biology. Daily is the habit loop.

That cadence has a cost that no one puts on the box. Go describes waking up feeling excellent, checking a recovery score of 67, and immediately feeling worse than he had 10 seconds earlier. His phrasing is that the number started arguing with his body and the number won.

That is the product working exactly as designed. It is engineered to be consulted, and a thing you consult every morning eventually becomes a thing you defer to. The device stops being an instrument and starts being an authority, and it acquires that authority without ever having earned it on accuracy.

The graduation problem

The honest value of a wearable is front-loaded. In the first few months you learn what wrecks your sleep and what fixes it. The culprits are usually not surprising: alcohol, very late meals, overly hot rooms, too much late-night screen time. You mostly know this.

The subscription, however, is perpetual. Which means a wearable company's core retention challenge and incentive is to keep charging you after the product has finished being informative. Every score, streak, badge, and daily insight is an answer to that challenge. When Go's Apple Watch broke on a surf trip in January he did not replace it. He went 5 months without any tracker and says his life got slightly better. He stopped outsourcing how he felt to a device.

That is the graduation problem, and it is backwards from how software normally works. In most subscription businesses the sophisticated user is the sticky one. Here the sophisticated user is the one most likely to take the thing off. Which tells you what all that engagement machinery is really for.

Why you should care

None of this makes wearables useless. It makes them badly specified.

An honest device would report sleep duration and trend and stop there, because that is what survives contact with a sleep lab. It would alert on extremes and otherwise stay quiet, which is the one use Go still respects: the time a temperature reading flagged an illness before he felt it. It would publish its validation data against polysomnography. And it would show you a confidence interval.

The best wearable is the one that changes a decision. Duration and trend change decisions. An extreme alert changes a decision. A daily breakdown with several notifications and a 76% spread across devices changes little except your mood.

If your device has not changed a decision in a month, you are not measuring your health. You are subscribing to a feeling.

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