Intersection cross-cut: sensor-ppg ∩ algo-hrv

Axes: sensors × algorithms

9 corpus entries disclose both tags.

Earliest disclosure: 1996-03

These entries are the direct inputs to OBVIOUSNESS_TEMPLATE.md. Any patent claim combining these two elements is anticipated or rendered obvious by the chain below.

Task Force of the ESC and NASPE (1996) — heart rate variability: standards of measurement (1996-03)

  • id: esc-naspe-1996-hrv-standards
  • corpus: standards
  • form factor: other
  • creator: Task Force of the ESC and NASPE
  • disclosure: Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. ‘Heart rate variability: standards of measurement, physiological interpretation, and clinical use.’ Circulation 1996;93(5):1043-1065 (also European Heart Journal 1996;17:354-381).
  • ip status: standards
  • sensors: sensor-ecg, sensor-ppg
  • algorithms: algo-hrv, algo-stress-index
  • prior art notes: Standardizes the time-domain (SDNN, RMSSD, pNN50, …) and frequency-domain (VLF/LF/HF, LF/HF ratio) measures of heart rate variability, their computation from an interbeat-interval series, and their physiological interpretation. Any wearable claim reciting ‘computing a heart-rate-variability metric (e.g. RMSSD, LF/HF) from a sequence of interbeat intervals’ rests on metrics standardized here. Anchor for the HRV cross-cut; applicable whether the interbeat intervals come from ECG or PPG.

Allen (2007) — ‘Photoplethysmography and its application in clinical physiological measurement’ (2007-02-20)

  • id: allen-2007-ppg-review
  • corpus: academic
  • form factor: other
  • creator: John Allen (Freeman Hospital / Newcastle)
  • disclosure: Allen J. ‘Photoplethysmography and its application in clinical physiological measurement.’ Physiological Measurement 2007;28(3):R1-R39. doi:10.1088/0967-3334/28/3/R01.
  • ip status: public-domain
  • sensors: sensor-ppg
  • algorithms: algo-hr, algo-hrv, algo-respiratory-rate, algo-spo2-estimation, algo-pwv-bp-estimation
  • prior art notes: Canonical review collecting the state of PPG measurement and the physiological parameters derivable from a PPG signal as of 2007 — heart rate, HRV, respiratory rate, SpO2, blood-pressure surrogates, arterial-stiffness/aging indices, vasomotor assessment. Relevant to wearable claims that recite ‘deriving [parameter X] from a photoplethysmography signal’ for any X covered here: the derivation was a published, enabled technique by 2007, defeating novelty of the bare derivation and supplying § 103 motivation for the form-factor+PPG+algorithm combinations. The single most-cited anchor for PPG-derived-metric wearable patents.

WHOOP Strap (2015) — display-less wrist/bicep PPG band for continuous HR/HRV, sleep and recovery (2015)

  • id: whoop-strap-2015
  • corpus: private
  • form factor: bracelet
  • creator: WHOOP, Inc. (Will Ahmed)
  • disclosure: WHOOP, Inc. ‘WHOOP Strap’, launched 2015 — a screenless band worn on the wrist or upper arm with photoplethysmography, a 3-axis accelerometer, and skin-temperature sensing, providing continuous heart rate, heart-rate variability, respiratory rate, sleep staging, and a derived ‘recovery’ score, with no on-device display.
  • ip status: patented
  • sensors: sensor-ppg, sensor-accelerometer, sensor-skin-temperature
  • algorithms: algo-hr, algo-hrv, algo-respiratory-rate, algo-sleep-staging, algo-activity-classification
  • prior art notes: Discloses a display-less band worn on the wrist or upper arm with PPG, accelerometry, and skin-temperature sensing that continuously derives HR, HRV, respiratory rate, and sleep stages and combines them into a daily ‘recovery’ index, with no screen (companion-app readout). Anticipates screenless-band claims and PPG-derived-HRV/recovery-score claims from 2015. Product-side anchor for the bracelet × PPG cross-cut and the HRV cross-cut.

Oura Ring (Gen 1, 2015) — finger-ring PPG, skin-temperature and accelerometer for HRV, sleep and body temperature (2015-08)

  • id: oura-ring-gen1-2015
  • corpus: private
  • form factor: ring
  • creator: Oura Health Oy
  • disclosure: Oura Health Oy. ‘Oura Ring’ (1st generation), crowdfunded 2015, shipped 2016 — a titanium finger ring with infrared photoplethysmography, an NTC skin-temperature sensor, and a 3-axis accelerometer, deriving resting heart rate, heart-rate variability, respiratory rate, sleep staging, and body-temperature trend.
  • ip status: patented
  • sensors: sensor-ppg, sensor-skin-temperature, sensor-accelerometer
  • algorithms: algo-hr, algo-hrv, algo-respiratory-rate, algo-sleep-staging
  • prior art notes: Discloses a finger-ring wearable with infrared PPG, a skin-temperature sensor, and an accelerometer, deriving resting HR, HRV, respiratory rate, sleep stages, and a body-temperature trend, with companion-app readout. A commercial realization, ~12-16 years later, of the MIT ring-sensor concept ([[asada-mit-wearable-ring-sensor-2003]]); to the extent later claims recite ring-form PPG + skin-temperature + HRV/sleep, both Asada 2003 and Oura 2015 are prior art. Product-side anchor for the ring × PPG × HRV and ring × skin-temperature cross-cuts.

Masimo W1 (2022) — first FDA-cleared continuous wrist medical-grade pulse oximetry watch (2022-05)

  • id: masimo-w1-2022
  • corpus: private
  • form factor: watch
  • creator: Masimo Corp.
  • disclosure: Masimo Corp. ‘Masimo W1’ health-tracking watch, announced May 2022 — a wrist-worn device performing continuous medical-grade pulse oximetry (SpO2), pulse rate, perfusion index (PI), pleth variability index (PVi), respiratory rate from the PPG, and HRV, using Masimo’s SET/rainbow signal-extraction algorithms. (FDA cleared as a continuous-monitoring medical device.)
  • ip status: patented
  • sensors: sensor-ppg, sensor-spo2, sensor-multi-wavelength-ppg, sensor-accelerometer
  • algorithms: algo-spo2-estimation, algo-hr, algo-hrv, algo-respiratory-rate
  • prior art notes: Discloses a wrist-worn device performing continuous medical-grade pulse oximetry — SpO2, PR, perfusion index, PVi, RR-from-PPG, HRV — using established signal-extraction methods, distinguished from consumer spot-check SpO2 by continuous operation and clearance for medical use. Anticipates wrist-continuous-medical-SpO2 claims from 2022; the underlying two-wavelength SpO2 method is much older ([[aoyagi-1974-two-wavelength-pulse-oximetry]], [[mendelson-ochs-1988-reflectance-pulse-oximetry]], [[iso-80601-2-61-pulse-oximeter-equipment-2011]]). Product-side anchor for the watch × continuous-SpO2 cross-cut.

Ultrahuman Ring AIR (2023) — smart ring with metabolic-focus tracking (PPG, skin temperature, IMU) (2023)

  • id: ultrahuman-ring-air-2023
  • corpus: private
  • form factor: ring
  • creator: Ultrahuman Healthcare Pvt. Ltd.
  • disclosure: Ultrahuman Healthcare Pvt. Ltd. ‘Ultrahuman Ring AIR’, launched 2023 — a titanium smart ring with infrared photoplethysmography, IR skin-temperature, and a 6-axis IMU, deriving HR, HRV, skin temperature, sleep staging, activity, and metabolic-health framing (paired with the company’s CGM-based metabolism platform).
  • ip status: patented
  • sensors: sensor-ppg, sensor-skin-temperature, sensor-accelerometer, sensor-gyroscope
  • algorithms: algo-hr, algo-hrv, algo-sleep-staging, algo-respiratory-rate
  • prior art notes: Discloses a smart ring with IR PPG, skin-temperature, and a 6-axis IMU, deriving HR/HRV, sleep, and activity, packaged with a metabolic-health platform (CGM-linked). Product-side reference in the ring × PPG cross-cut alongside [[oura-ring-gen1-2015]] and [[samsung-galaxy-ring-2024]].

HealthyPi Move (ProtoCentral, 2026) — open-source medical-grade smartwatch (2024)

  • id: healthypi-move-2026
  • corpus: open
  • form factor: watch
  • creator: ProtoCentral Electronics
  • disclosure: ProtoCentral Electronics (Bengaluru, India). ‘HealthyPi Move’ fully open-source AMOLED smartwatch — Crowd Supply campaign launched 2024, units shipping 15 May 2026. Sensors: single-lead ECG, dual-site PPG (wrist + finger), SpO2, blood-pressure trending, EDA/GSR, heart rate, HRV, respiration rate (derived), body temperature, 6-axis IMU. Compute: Nordic nRF5340 (dual ARM Cortex-M33). Display: AMOLED, 300 mAh battery. Companion app: Flutter, runs on Android/iOS/macOS/Windows/Linux, all data stored locally. Hardware design, firmware (Zephyr RTOS on nRF Connect SDK), and companion app all open-source. https://www.crowdsupply.com/protocentral/healthypi-move
  • ip status: open-permissive
  • sensors: sensor-ecg, sensor-ppg, sensor-spo2, sensor-multi-wavelength-ppg, sensor-gsr, sensor-accelerometer, sensor-gyroscope, sensor-skin-temperature
  • algorithms: algo-hr, algo-hrv, algo-spo2-estimation, algo-respiratory-rate, algo-pwv-bp-estimation, algo-sleep-staging, algo-activity-classification, algo-step-count
  • prior art notes: Discloses, as fully open-source hardware and firmware (CC and MIT-style licensing across components), a wrist-worn smartwatch with the full consumer-medical sensor stack: single-lead ECG between back-of-watch electrode and a finger-touch electrode; multi-wavelength reflectance PPG with SpO2 and BP-trending; EDA/GSR; skin temperature; 6-axis IMU; on-device Zephyr-RTOS application; AMOLED display; all-local data storage via cross-platform Flutter app. Anticipates wrist-multi-sensor-watch claims from 2024-2026 to the extent they recite combinations of these elements; as open prior art it is unencumbered and any patent claim reciting these combinations must distinguish over HealthyPi Move’s specific implementation. The product-side anchor for the ‘open watch with the full sensor stack’ cross-cut.

CogWatch (HardwareX, 2024) — open-source smartwatch for cognitive-load monitoring (2024)

  • id: cogwatch-2024-hardwarex
  • corpus: academic
  • form factor: watch
  • creator: (See HardwareX publication for full author list.)
  • disclosure: ‘CogWatch: An open-source smartwatch platform for cognitive-load monitoring.’ HardwareX 19 (2024). Open-source smartwatch design — full hardware, firmware, and assembly documentation published in the open-hardware-focused journal HardwareX (Elsevier). https://www.hardware-x.com/article/S2468-0672(24)00032-4/fulltext
  • ip status: public-domain
  • sensors: sensor-ppg, sensor-gsr, sensor-accelerometer
  • algorithms: algo-hr, algo-hrv, algo-stress-index, algo-cognitive-workload
  • prior art notes: Discloses, as open-hardware (HardwareX is the canonical venue for full publication of open-hardware designs), a wrist-worn smartwatch instrumented for cognitive-load monitoring from PPG-derived HRV and EDA/GSR. Prior art for smartwatch-cognitive-load claims combining ‘a wrist-worn device’, ‘PPG and EDA sensors’, and ‘a derived cognitive-load metric’ from 2024.

Samsung Galaxy Ring (2024) — smart ring with PPG, skin temperature and accelerometer for HR/HRV, sleep and cycle tracking (2024-07-10)

  • id: samsung-galaxy-ring-2024
  • corpus: private
  • form factor: ring
  • creator: Samsung Electronics Co., Ltd.
  • disclosure: Samsung Electronics. ‘Samsung Galaxy Ring’, announced July 2024 — a finger ring with infrared photoplethysmography, an IR skin-temperature sensor, and a 3-axis accelerometer, deriving heart rate, heart-rate variability, skin temperature, sleep staging, activity, snore detection, and (with cycle-tracking) menstrual-cycle predictions.
  • ip status: patented
  • sensors: sensor-ppg, sensor-skin-temperature, sensor-accelerometer
  • algorithms: algo-hr, algo-hrv, algo-respiratory-rate, algo-sleep-staging, algo-snore-detection, algo-step-count
  • prior art notes: Discloses a smart ring with infrared PPG, IR skin-temperature, and accelerometer, deriving HR/HRV, sleep, snore detection, activity, and menstrual-cycle prediction — a Samsung entry directly in the wake of [[oura-ring-gen1-2015]] and the [[asada-mit-wearable-ring-sensor-2003]] academic root. Product-side reference in the ring × PPG × HRV cross-cut alongside Oura.

Public domain (CC0 1.0). The corpus IS the prior art commons.

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