Research: The Body-Layer Firms — Dexcom's Stelo, Precision Neuroscience and Mount Sinai
The first over-the-counter glucose monitor, cleared for people who are not sick; the least-invasive brain implant on the market and what its 510(k) does and does not allow; and the hospital where more than one company's brain data is collected. FDA records first, with the clearance numbers checked against the database.
Contents
Companion pages: The Body Layer, the Neuralink profile and Healthcare Data.
Three firms carry the body-layer argument from the bloodstream to the brain. Every regulatory fact below is from the FDA’s own announcement or its device database; company figures are the companies’ own.
1. Dexcom’s Stelo: continuous body data for people who are not patients
What it is. In the FDA’s words, the Stelo Glucose Biosensor System “uses a wearable sensor, paired with an application installed on a user’s smartphone or other smart device, to continuously measure, record, analyze and display glucose values in people 18 years and older that are not on insulin and who do not have problematic hypoglycemia. Users can wear each sensor up to 15 days,” with readings every 15 minutes (FDA, Mar 5 2024).
The first of its kind. It was the first continuous glucose monitor the FDA cleared without a prescription: “FDA Clears First Over-the-Counter Continuous Glucose Monitor,” March 5, 2024. Dexcom: “Stelo will be the first glucose biosensor in the US cleared for use without a prescription” (Dexcom). The clearance is 510(k) K234070, applicant Dexcom, decision March 5, 2024 (openFDA). A later Stelo clearance, K261359 (May 2026), is a subsequent version.
Everyone’s a patient. The point is in the clearance itself. The FDA describes Stelo as “intended for anyone 18 years and older who does not use insulin, such as individuals with diabetes treating their condition with oral medications, or those without diabetes who want to better understand how diet and exercise may impact blood sugar levels.” Dexcom sized the market at “approximately 25 million people in the U.S. living with Type 2 diabetes who do not use insulin,” plus the wellness buyers. A disease-management device became an always-on sensor for the healthy, with the regulator’s blessing.
Launch. It went on sale on August 26, 2024, “for as low as $89.99 for a 2-pack” of sensors, a month’s wear (HCPLive, Aug 26 2024); press reports give $99 for a one-time two-pack and $89 a month by subscription.
2. Precision Neuroscience: the least-invasive brain implant, and what its clearance allows
The device. Layer 7 is “a high-resolution cortical electrode array, for use in the recording, monitoring, and stimulation of electrical activity on the surface of the brain”: 1,024 electrodes on a film thinner than a hair, laid on the brain’s surface without penetrating it, “minimally invasive, safely removable” (Precision, Apr 17 2025). That is the contrast with Neuralink’s threads, which go into the cortex.
The clearance, exactly. 510(k) K242618, device “Layer 7-T,” decision March 30, 2025, “Substantially Equivalent” (openFDA); the company announced it on April 17. It authorizes “commercial use with implantation durations of up to 30 days.” A 510(k) says a device is substantially equivalent to one already on the market. It is not approval of a permanent brain implant for general use.
Who runs it. Precision was founded in 2021; its chief science officer, Benjamin Rapoport, is in the company’s words “a neurosurgeon-engineer and former co-founder of” Neuralink; Michael Mager is chief executive (Precision, Dec 16 2024).
The money. A $102 million Series C in December 2024, led by General Equity Holdings with B Capital and Stanley Druckenmiller’s Duquesne Family Office (same release). Then, on September 25, 2026, a $250 million oversubscribed Series D co-led by Bill Ackman’s Pershing Square and the Ackman Oxman Institute, with Duquesne, B Capital, ARK Invest and Invus. Ackman: “We have learned that the brain can recover from even catastrophic injury, and that there is far more that can be done for people living with neurological injuries … Neurotechnology will be central to the next generation of cures, treatments, and rehabilitation” (MassDevice, Sep 25 2026).
Scale. By the clearance, Precision said it had tested Layer 7 in 37 patients with Mount Sinai Health System, the University of Pennsylvania, West Virginia University’s Rockefeller Neuroscience Institute and Beth Israel Deaconess, beginning in June 2023.
3. Mount Sinai: the room where brain data is collected
The first US Stentrode. In July 2022 Mount Sinai performed the first US implant of Synchron’s Stentrode, led by Dr. Shahram Majidi, in a 67-year-old man with ALS: the device went in through the jugular vein to the superior sagittal sinus beside the motor cortex, with no open-brain surgery, under “the first investigational device exemption (IDE) awarded to a company assessing a permanently implanted BCI” (NeuroNews International, Aug 26 2022).
A host for more than one company. Mount Sinai is also one of the four institutions where Precision tested Layer 7 (above). It is the place where several companies’ brain-data collection actually happens, which is why the question of who has administrative access to an implanted brain runs through it. It is a research host and partner, not a device owner.
The argument
The bloodstream and the brain are being instrumented by the same sequence: a medical device for the sick is cleared, then the indication widens. Stelo crossed that line in 2024, when a regulator cleared continuous telemetry for people with no disease. The brain implants are earlier in the sequence, cleared for 30 days of recording in patients, but they are funded at a scale (a $250 million round in 2026) that assumes they will not stay there.