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Health technology, privacy-first design, and the research behind what a ring can actually measure.

A person running on a treadmill in a lab setting, the exact environment where Stanford tested fitness trackers against clinical calorimeters

Latest Activity & Movement · Research, Explained Why Your Wearable's Calorie Count Is Wrong by 27 to 93 Percent A Stanford study tested seven fitness trackers against clinical instruments. Heart rate was accurate. Energy expenditure was off by 27 to 93 percent on every device. The calorie number on your screen is not a measurement. It is a guess. James Hoffmann May 30, 2026 15 min read Read article

Why the Smart Ring Form Factor Is Better for Sleep Than the Wrist: A Physics Argument James Hoffmann May 29, 2026 13 min read

Oura Ring 5 Is $499. Here Is What Three Years Actually Costs. Oura launched the Ring 5 at $499 with a mandatory subscription and a new AI coach fee. Over three years, the cheapest configuration totals $715. Here is the math, and why Pulsyn is building the alternative. James Hoffmann May 29, 2026 12 min read

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LATEST ARTICLES

Thermal imaging of a human hand showing heat distribution. The kind of raw signal most smart rings average away

What Skin Temperature Actually Tells You (And Why Most Rings Get It Wrong) Skin temperature is a proxy for blood flow, circadian phase, and autonomic tone. Most smart rings average it into a single nightly number. We do not. James Hoffmann May 28, 2026 14 min read

A medical pulse oximeter clipped to a fingertip, using transmissive light technology that consumer smart rings cannot replicate

Why Your Smart Ring SpO2 Reading Is Probably a Guess Consumer wearables run reflective PPG on body parts never designed for it. The FDA has scrutinized these monitors since 2022 for systematic bias. Smart rings compound the problem with clamp pressure and unvalidated algorithms. James Hoffmann May 28, 2026 11 min read

A hardware workshop with tools and prototype components on a workbench

A $500K Kickstarter Is the Most Honest Milestone in Hardware Most hardware startups take VC money before they know if anyone wants their product. Pulsyn's $500K Kickstarter campaign is a demand test with no safety net. James Hoffmann May 27, 2026 11 min read

Abstract digital privacy visualization representing encrypted health data that never leaves your device

Your Fertility Data Is Evidence Now In a post-Dobbs United States, fertility data from wearables has entered criminal prosecutions. Oura stores cycle data on AWS. Whoop stores it on their own servers. Pulsyn stores it on your phone, encrypted, with no cloud account. James Hoffmann May 27, 2026 13 min read

A gavel resting on a courtroom bench, representing how digital health data from fitness trackers is now routinely admitted as evidence in legal proceedings

Your Fitness Tracker Is Evidence: How Health Data Ends Up in Courtrooms and Divorce Filings Your fitness tracker records everything. That data lives on someone else's server, and in at least one murder trial, it was the evidence that convicted the killer. Here's how health data ends up in courtrooms, divorce filings, and subpoenas — and why Pulsyn's local-first architecture makes the difference. James Hoffmann May 26, 2026 13 min read

A customs inspection checkpoint at a border crossing — where Ultrahuman Ring Pro just cleared after months blocked by Oura patent disputes

Ultrahuman Ring Pro Lands in the US at $479 Ultrahuman Ring Pro just cleared US customs after an Oura patent block and is selling at $479 with no subscription. That price validates Pulsyn's entire thesis: on-device health tracking should not cost more than a flagship smartphone. James Hoffmann May 26, 2026 11 min read