Under-Mattress vs Bedside Radar Sleep Tracker: What the Studies Show (2026)

Same night, two shelves. A pad under the mattress reads motion through the bed. A radar on the nightstand reads reflections from the chest. Lab papers compared specific devices, not the whole category.

Disclosure: I am Dovy, founder of Komori Care. We are building a contactless bedside sleep monitor, coming 2027, wellness only.

Quick answer

• In a sleep-lab study of older adults (JMIR, doi 10.2196/46338), Somnofy radar had stronger sleep/wake agreement (MCC 0.63) than Withings Sleep Analyzer (0.41) and Emfit QS (0.35). Those are those three devices on that protocol, not a ranking of every mat or every radar.
• A second aging study (JMIR mHealth, PMC11387924) found the under-mattress devices measured heart rate and breathing. The Somnofy radar measured breathing only. Somnofy's nightly breathing-rate MAPE against PSG was 4.64%.
• Rule of thumb: under-mattress if a heart-rate trend matters, bedside radar if you want sleep and wake timing with nothing under the sheet.
• Komori Care (coming 2027, wellness only): bedside 60GHz radar with no camera, designed for a back/side/stomach position timeline, not an under-mattress mat.

If you already picked a mat, see Sleep Number alternatives that keep your mattress. For the number tables, see how accurate radar sleep trackers are.

What the first lab night showed

Thirty-five older adults, first night in a lab, ten-hour time in bed. PSG was the reference. All three contactless devices overestimated total sleep time (bias over 90 minutes) and under-called wake after sleep onset. Somnofy was closer on sleep onset. Accuracy of REM and light sleep was poor across all three. That paper is also on PMC as PMC10632916.

Do not turn those MCCs into "radar is always better." The devices, the age group and the first-night protocol are the claim.

Heart rate vs breathing

PMC11387924 used the same three products. Withings and Emfit produced heart rate. Somnofy did not. Breathing rate was available from all three. Nightly average heart-rate MAPE was under 5% for the mats. Nightly breathing MAPE was 4.64% for Somnofy, 6.29% for Withings and 5.46% for Emfit.

Neither paper says these devices separate REM from light sleep reliably. The first paper is blunt about stage labels.

Setup and toppers

Under-mattress: slide the pad in once. OZI says toppers up to about 4 inches. Withings says spring, foam or latex is fine and flags waterbeds and air mattresses.

Bedside: aim at the chest. Hatch says the clock sits on the nightstand and reads breathing and movement from a few feet away.

Who it follows

Withings says the Sleep Analyzer focuses on the person resting directly above it. Hatch says Sleep Clock follows one primary sleeper. Nest Hub Sleep Sensing is one calibrated person. See sleep trackers for couples.

Komori Care (coming 2027)

Komori Care is on the bedside-radar side of this split: 60GHz above or beside the bed, nothing to wear, no camera required, aimed at a back, side and stomach timeline. Coming in 2027, wellness only. We are not claiming it matches any study above.

FAQ

Which is more accurate? Cite the study. Somnofy led on sleep vs wake MCC in that older-adult lab night. The mats measured heart rate and the radar in that pair did not. Those are specific devices.

Does a thick topper matter? OZI says up to about 4 inches. Withings lists waterbeds and air mattresses as the problem cases.

Which works for two people? Withings Sleep Analyzer and Nest Hub follow one person. Hatch follows one primary sleeper. See the couples guide.

Which is easier to set up? Under-mattress: slide in once. Bedside: aim it at the chest.

Can Komori Care go under the mattress? No. Komori Care (coming 2027, wellness only) is bedside 60GHz radar, designed to sit above or beside the bed.

Keep reading

• How accurate are radar sleep trackers?
• Sleep Number alternative for sleep tracking
• Best under-mattress sleep tracker
• Bedside sleep tracker alternatives
• Privacy: bedside vs under-sheet
• Sleepal vs Withings Sleep
• Sleep tracker validation scoreboard

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Komori Care is a contactless sleep monitor in development. Camera-free position tracking, coming 2027. Wellness only. Join the waitlist.