The best under-mattress sleep trackers: sleep data with nothing on your body

Why track sleep with nothing on your body

This site exists because people want recovery data without a watch. An under-mattress tracker is the logical end of that argument: nothing on your wrist, nothing on your finger, nothing to size, nothing to charge and nothing to forget.

Four practical advantages over any wearable:

• No charging, ever. These run on mains power. A sleep tracker that needs charging has to be charged while you are awake, which is the one habit that puts holes in a sleep record.
• No sizing. No sizing kit, no wrong size, no returns. Our sizing guide exists because getting a ring wrong is the most common expensive mistake in this category, and a mat skips it entirely.
• It can hear you. A microphone under the bed can count snoring episodes and flag breathing disturbances. No ring has a microphone, so no ring can do this at all.
• Nothing touches your skin. If a ring or a band irritates you, or your job or hobby rules out jewellery on your hands, this is the category for you.

The cost is obvious and worth saying up front: a mat only knows about your own bed. No naps on the sofa, no hotel nights, no daytime heart rate, no activity, no workouts.

The fee shift nobody announced

Here is what each required plan costs over one, three and five years, with a ring and Oura for scale.

The Emfit QS is deliberately absent from that table. Its service fee is quoted in euros on a Finnish-language ordering page, and we do not print converted figures - every number on this site links to a source. Take the euro figure from Emfit's page, convert it yourself on the day, and remember three years are included at purchase. Our subscription cost breakdown runs the same arithmetic for every brand whose US fees we could verify.

How a mat measures a heartbeat through a mattress

The method is called ballistocardiography, and it is older than any of these products: your heartbeat and your breathing move your body very slightly, and those movements travel through a mattress as mechanical vibration. A sensitive enough sensor underneath can read them.

Withings describes its own implementation precisely: a pneumatic sensor that “measures your heart and respiratory rates as well as your movements through the mattress using ballistography,” plus a sound sensor that “identifies audio signals specific to snoring and breathing disturbances.” Emfit uses an electroactive film it develops and manufactures itself, which works without power of its own, with the electronics on a long cable so the transmitter can sit away from the bed.

Two things follow. First, nothing here reads blood oxygen, temperature or HRV from your skin - it is all inferred from movement, so do not expect the same metric list as a ring. Second, it is sensitive to your bed: Withings supports spring, foam and latex mattresses, says it “is not intended to be used with water mattresses,” and notes air mattresses may affect accuracy.

How we ranked them

These are scored on a rubric of their own, because the ring rubric's “Battery (claimed)” is meaningless for a mains-powered mat and scoring it would flatter the product. The sleep-tracker rubric keeps the same weights: cost of ownership over three years (30%), evidence of accuracy (25%), setup and upkeep (15%), who it suits - bed, partner, mattress - (10%), data ownership (10%) and platform support (10%). It is published in full on our methodology page.

Every pick is labeled Researched, and the evidence scores are low across the board for a reason we explain below.

The picks in context

1. Withings Sleep — the one to buy

A 637 x 190 x 5 mm fabric-covered mat weighing 350 g, powered by an included 5V 1A USB adapter, that goes under the mattress and then never asks anything of you again. It reports sleep cycles (deep, light, REM), sleep duration, onset and wake time, continuous and average heart rate, snoring episodes and their duration, breathing disturbances and a Sleep Score. It syncs over 2.4 GHz Wi-Fi by itself, stores data locally between syncs, and Withings gives “free and unlimited online data storage with a Withings account” plus Apple Health, Google Health Connect and Google Fit compatibility and a web dashboard.

Two details we like. Withings says it “is engineered to focus exclusively on the person resting directly above it. It does not capture the movements or heart rate of a partner” - the single most common worry about bed sensors. And it claims development “in collaboration with sleep physicians from Hopital Beclere in Paris” with testing “against data obtained by polysomnography (PSG) analysis.” That is a maker's claim rather than a named, published study, which is why its evidence score is middling rather than high.

Limits: setup needs a phone and cannot be done from a computer, it is not for waterbeds, air mattresses may affect accuracy, and the Readiness Indicator is behind Withings+. It is listed on Amazon.com as well as Withings' own store.

2. Emfit QS — the athlete's choice, with an asterisk

The Emfit QS does one thing better than anything else here: HRV across the entire night rather than a single morning reading, with evening and morning values and a recovery and readiness analysis built on them. Emfit's pitch is squarely at athletes managing training load. It needs no phone at all - the collection unit has its own processor, memory and internet connection, and you read the data in a browser. On data ownership it says the right things: users keep ownership of their personal data, it is not shared with third parties, data is retained for a year after the last paid period so you can view, download or delete it, and an optional Push API is included.

Then the asterisk. Emfit says the QS was previously sold for a one-time payment and that since March 2024 it ships with a fixed-term cloud service - three years included, then a yearly fee - and that without an active subscription the cloud service and sleep-tracking features are not available. It is ordered from Finland, priced in euros, with import charges on you, and the ordering page is in Finnish. There is no named validation study and nothing published about how a partner in the bed affects readings.

For a reader who came to this site to stop renting their own data, that is a hard sell. It earns second place on capability, not on terms.

3. Eight Sleep Pod 6 — a climate system that also tracks

Worth understanding for what it is: primarily a temperature system. The Pod is a cover that fits over your existing mattress “like a fitted sheet,” with a Hub (16.54 x 7.87 x 6.50 in, 15.2 lbs, 120/240V AC in, 550W 12V DC out) that cools and heats each side of the bed from 55F to 110F, wakes you with thermal and vibration alarms, and tracks per-side sleep while it does. It comes with a 5-year warranty and a 30-night risk-free trial, and per-side tracking for two people is genuinely useful.

The problems, from this site's point of view: an Autopilot plan at $299/year is folded into the purchase price and keeps billing; Eight Sleep's page does not state what the Pod does once it lapses; the tracking claim is “clinical-grade sensors” with no published validation and no stated sensing method; and it is bedroom furniture - a hub, a water cord and a cover. If temperature control is what you actually want, nothing else here offers it. If sleep data is what you want, you are paying a lot for it.

Side by side

Two head-to-heads go deeper than this ranking does. The two devices most people end up choosing between are compared in full on Withings Sleep vs Eight Sleep Pod 6. And if you would consider wearing something after all - just not on a finger - Garmin Index Sleep Monitor vs Oura covers the night-only arm band.

A mat or a ring?

Straight comparison, because most readers of this page are choosing between the two categories rather than within one.

Choose a mat if: you will not wear anything to bed, your hands rule out a ring, sizing worries you, snoring or breathing disturbances are the thing you actually want measured, or you want zero charging.

Choose a ring if: you travel, you nap anywhere but your own bed, you want daytime heart rate and activity too, you share a bed and want certainty the data is yours, or you want the strongest published accuracy evidence. Our best smart ring for sleep tracking ranks that side, and best sleep tracking wearables covers the non-ring wearables.

On fees, the comparison is closer than you would expect. A Withings Sleep charges nothing required, exactly like a RingConn Gen 2, and an Oura membership costs $209.97 over three years. So this is not a cheap-versus-expensive decision; it is a what-will-you-actually-wear decision.

The FDA-cleared one you cannot just buy

If you are here because you suspect sleep apnea, there is a device in this category with real clearance, and it is not on a shop shelf. Withings' Sleep Rx received FDA 510(k) clearance in September 2024 as a contactless, under-mattress device intended to aid in diagnosing obstructive sleep apnea at home - no wearable sensors, wires, masks or straps. It uses a pneumatic sensor to measure respiratory rate, body movement and heart rate, with sound and motion detection for snoring and breathing disturbances (Sleep Review, AASM).

The catch is the route to it: Sleep Rx is available in the US by prescription, through healthcare professionals via Withings Health Solutions, as part of clinical sleep management or remote patient monitoring programs. You cannot order one the way you order the consumer mat. That is the correct arrangement for a diagnostic device, and it is also the clearest possible illustration of the line between a wellness gadget and a cleared medical device. Our smart ring sleep apnea guide covers what the consumer devices are and are not allowed to claim.

What to check before you buy

1. Whether the tracking survives cancellation. The single most important question in this category. Withings says your sleep history and trends stay free; Emfit says the features are unavailable without an active subscription; Eight Sleep does not say.
2. Your mattress. Withings supports spring, foam and latex, rules out waterbeds and warns about air mattresses. Check your own before ordering.
3. Your bed partner. Withings says it reads only the person above it. Emfit does not address it. Eight Sleep tracks each side separately by design.
4. Wi-Fi at the bed. Withings needs 2.4 GHz Wi-Fi and a phone for setup, and cannot be installed from a computer. Emfit needs 2.4 GHz Wi-Fi too, but no phone at all.
5. Where the data goes. All three are cloud services. Withings offers free unlimited storage plus Apple Health and Google Health Connect sync; Emfit states you retain ownership and offers a Push API. Our data privacy guide covers what to look for in any of these policies.
6. HSA/FSA. Withings' page flags HSA/FSA eligibility and Eight Sleep lists an HSA/FSA payment option. Your plan administrator decides - see our HSA/FSA guide.

Mistakes to avoid

• Assuming a mat is a one-time purchase. It used to be a safe assumption in this category. Emfit changed that in March 2024, and Eight Sleep never offered it.
• Buying an under-mattress tracker if you travel. It cannot follow you. A ring can.
• Expecting ring metrics. No blood oxygen, no skin temperature, no daytime activity. The metric list is genuinely different.
• Reading “clinical-grade” or “tested against PSG” as FDA clearance. The only FDA-cleared device in this category that we found is prescription-only.
• Buying a climate system when you wanted a sleep tracker. The Eight Sleep Pod is excellent at the thing it is really for. If that thing is not temperature control, it is a very expensive way to log a night.
• Buying it to diagnose something. These are wellness devices. A breathing-disturbance count you can show a doctor is useful; a diagnosis is the doctor's.