HB-1 · Smart hydration ring
Five sensors read fluid levels through your finger, all day, with nothing to stick on and nothing to remember. One number, and one instruction: how much to drink, and by when.
Free sizing kit ships first. No subscription, ever.
HYDRATION LOW · DRINK 400 ML
The landscape
This is the honest version of the competitive picture, and it is a better argument than pretending nobody got here first. Three approaches are on the market. Each one works. Each one stops working the moment you forget about it.
Sweat patches
Microfluidic adhesive patches that read sweat chemistry during exercise. Genuinely good science, validated in athletes, and the closest thing to a real measurement on the market.
Single use. They only read while you are actively sweating, and every session costs another patch.
Spot-check bioimpedance
An Apple Watch band that runs bioimpedance to estimate body water. Same underlying method HydroBand uses, and proof the measurement can be miniaturised.
You open an app and hold your palm to the band for about 30 seconds. Nothing is measured unless you decide to measure it.
Continuous, on your hand
Bioimpedance and sweat sensing on a ring that is already on your finger for sleep and heart rate. Sampled through the day, with no patch, no consumable, and no scan to remember.
The trade is battery. Five to seven days, against eleven or more for rings that measure less.
COMPETITOR CAPABILITIES SUMMARISED FROM PUBLISHED PRODUCT DOCUMENTATION AND INDEPENDENT REVIEWS, JULY 2026.
Who it is for
Dehydration is not the universal crisis the internet claims it is. The often-quoted line that three quarters of Americans are chronically dehydrated has no support in the medical literature. What is documented is prevalence between 17 and 28 percent among older adults in the United States, and a well-established performance cost in people who sweat for sport or for pay. Those are the people we sell to first.
TAM · Total addressable
Roughly 600 million wearable users worldwide. At a $250 device that is the ceiling if hydration sensing ever became a standard feature on everything.
Nobody wins a TAM. It is context, not a plan.
SAM · Serviceable
About 50 million people who sweat on purpose or for pay: athletes, runners, gym members, outdoor trades, military, firefighters, and police.
Still far more than we can reach in five years.
SOM · Realistically obtainable
About $2.5B of annual hardware revenue at full penetration. That is a fifth of the entire SAM, which is an aggressive claim for a product that has not shipped yet and worth treating as a ceiling, not a plan.
This is the figure the financial model is built on.
Primary customer
Sarah, 29, a physical therapist in Denver earning $72,000. She is in the gym five days a week and trains for half marathons on weekends. She already wears an Apple Watch, so she is not a hard sell on wearables. She simply forgets to drink, and finds out about it eight miles into a long run.
Where we reach her
Running and hiking creators and dietitian coaches first, alongside college athletic programs. Then gym chains, running clubs, and marathon and triathlon organisers. Outdoor and sporting goods retail comes last, once the brand can hold a shelf on its own.
How it works
Fingers are dense with capillaries and sweat glands. A ring also holds its sensors flat against skin far more consistently than a watch band does, because a ring cannot slide. That is the whole reason this is a ring.
01 · SENSE
Two gold electrodes measure bioimpedance and sweat activity. An optical sensor reads heart rate and variability. A thermistor tracks skin temperature. A 6-axis motion sensor catches workouts.
02 · LEARN
A one-minute setup survey seeds the model. Two weeks of wear teaches it your resting fluid level, your typical sweat rate, and how fast you come back after a hard session.
03 · SCORE
A model on your phone combines the sensor data with your workouts and the local weather into a score from 0 to 100. It reports movement against your own baseline rather than an absolute body water figure, which is the part the science actually supports.
04 · ACT
"Drink 400 ml in the next 30 minutes." If your phone is out of range, the ring runs a smaller model on its own hardware and flashes the light band.
The app
Should I drink right now? Every other screen exists to make that answer accurate.
Press Alert on the model above, then look back at the phone. The light band and the app change together, which is how the real pairing behaves.
On track · 6% under your baseline
DOUBLE-TAP THE RING TO LOG HANDS-FREE
Weekly average: 71. Your baseline drifted down 2% during the heat wave, which is normal. Your worst window is 2 to 5 PM. A standing 300 ml at lunch would flatten it.
Saturday read low all afternoon. Salt water masks sweat readings, so the score leaned on bioimpedance instead.
Interactive · tap the tabs
Engineering
A 22 mAh curved cell spans 140 degrees of the band. A flex circuit carries the compute around the rest. Then the cavity is filled solid with epoxy, which is also the waterproofing. Switch the model above to Inside to see the layout.
The battery is the entire design constraint. Bioimpedance runs on a fifteen-minute duty cycle instead of continuously. That is the difference between five days and two.
22 mAh curved cell
Five to seven days at roughly 0.6 grams. It sets the sampling budget for every sensor on the board, and it is the reason this ring lasts a week instead of two.
Bluetooth 5.3 SoC
Radio and microcontroller in one package. It also runs the small threshold model that fires alerts when your phone is not around.
Gold electrodes ×2
Bioimpedance and sweat activity share the same two contacts, sampled in different modes.
BIA and EDA front end
Drives a microcurrent through finger tissue and reads what comes back.
Optical module
Resting heart rate climbs and variability drops as fluid falls. This catches both.
NTC thermistor
Skin temperature, pressed against the inner liner for heat strain context.
6-axis motion sensor
Detects workouts, and reads the double-tap that logs a drink.
16 MB flash
Holds your baselines and buffers two weeks of readings. Capacity is not the limit here. Policy is.
Two-track charge pads
Concentric gold contacts on the bottom edge meet two pogo pins in the case. The ring docks at any rotation, so there is no alignment to get right. No port and no coil.
Titanium and epoxy
A grade 5 titanium shell over a fully potted medical grade epoxy interior. It is the same construction the category has settled on, and it is why a ring with no openings can be rated to 100 metres.
Specifications
| Ring | Hardware | Subscription | Three-year cost | Battery | Hydration |
|---|---|---|---|---|---|
| HydroBand HB-1 | $250 | None | $250 | 5 to 7 days | CONTINUOUS |
| Oura Ring 4 | From $349 | $5.99 / month | About $559 | 5 to 8 days | None |
| Samsung Galaxy Ring | $399 | None | $399 | Up to 7 days | None |
| RingConn Gen 3 | About $349 | None | About $349 | 11 to 14 days | None |
| Ultrahuman Ring AIR | About $349 | None | About $349 | Up to 6 days | None |
PRICING AND SPECIFICATIONS COMPILED FROM MANUFACTURER DOCUMENTATION AND INDEPENDENT REVIEWS, JULY 2026. OURA THREE-YEAR FIGURE IS $349 PLUS THIRTY-SIX MONTHS OF MEMBERSHIP AT THE ANNUAL RATE. RINGCONN AND ULTRAHUMAN PRICES MOVE OFTEN. CONFIRM BEFORE ANY EXTERNAL USE.
For investors
Hydration sensing is real and it works. What it has never been is passive. Every product that measures it well asks the user to do something first: apply a patch, open an app, hold still for thirty seconds. We are betting the category is won by whoever removes that step, not by whoever invents the sensor.
Projected 2026 to 2030, with growth easing from 19 percent to 14 percent a year as the base gets larger. EBIT margin holds at 38 percent across the period.
The discounted cash flow estimate off those same five years, at a 15 percent discount rate and 2 percent terminal growth. This is the number the model actually computes, not a rounder headline figure.
Blends the DCF result with public comparables. WHOOP and Oura are both private, so the comparable multiples come from PitchBook rather than public filings.
Revenue and returns
| Line | 2026 | 2027 | 2028 | 2029 | 2030 |
|---|---|---|---|---|---|
| Revenue | $32,418 | $38,243 | $44,615 | $51,465 | $58,692 |
| Revenue growth | 19% | 18% | 17% | 15% | 14% |
| EBIT | $12,389 | $14,615 | $17,050 | $19,668 | $22,430 |
| EBIT margin | 38% in every year of the projection | ||||
A flat 38 percent EBIT margin from year one is the assumption we would defend hardest under questioning. Most hardware companies lose money while a first production run is finding its footing. This model does not build in that period, and an investor is right to ask why.
Valuation
| Method | Enterprise value |
|---|---|
| Discounted cash flow (15% discount rate, 2% terminal growth) | $159.8M |
| Public comparables, WHOOP (9.8x revenue) | not broken out |
| Public comparables, Oura (12.2x revenue) | not broken out |
| Selected valuation | $203.7M |
WHOOP and Oura are both private, so their multiples come from PitchBook rather than a public filing, and the split between the DCF figure and the comparable-driven uplift to $203.7M is not shown on the slide it came from. Worth having that reconciliation ready before someone asks for it directly.
Investor return
| Metric | Value |
|---|---|
| Entry enterprise value | $159.8M |
| Projected exit enterprise value | $238.5M |
| Gross MOIC | 1.89x |
| Annualized return | 15.0% |
Exit paths
Once revenue growth and international expansion are established, HydroBand could list publicly to fund further R&D and healthcare partnerships. This is the slower, more capital-intensive path and depends on the category still being investable at that point.
A wearable or health technology company (the kind of buyer Apple, Samsung, or Google represent) could acquire HydroBand to add hydration sensing to an existing ecosystem rather than build it in-house. This is the more common outcome for hardware startups at this scale and is worth naming as the base case, not just the IPO story.
What could kill this
Whole-body bioimpedance runs electrodes hand to foot. We are reading a single finger, which is a much shorter path and a noisier one. The literature also shows bioimpedance tracks change in hydration better than it measures an absolute figure, and there is still no agreed protocol for assessing hydration in athletes. That is why the score is relative to your own baseline, and why the validation study is the first thing we fund rather than the last.
Ultrahuman's Ring AIR is under a US import ban following its patent dispute with Oura, and RingConn settled by taking a licence. Oura itself raised at an eleven billion dollar valuation in late 2025 and filed confidentially for an IPO in May 2026. Any ring we ship in the United States needs a freedom-to-operate review and a licensing budget before tooling, not after.
Oura or Samsung can add an electrode pair to the next revision. The hardware was never the moat. The labelled dataset and a two-year head start are, and both of those expire.
A flat 38 percent EBIT margin from year one and a SOM equal to a fifth of the entire SAM are both optimistic relative to how early-stage hardware companies actually perform. Neither breaks the story, but both are the first things a diligence process will stress-test.
FINANCIAL FIGURES FROM THE HYDROBAND DISCOUNTED CASH FLOW MODEL, 2026 TO 2030. COMPARABLE MULTIPLES PER PITCHBOOK, PRIVATE-COMPANY ESTIMATES. PROJECTIONS ARE MANAGEMENT ESTIMATES, NOT CONFIRMED INPUTS. REGULATORY SUMMARY IS NOT LEGAL ADVICE.
Questions
No. It suggests fluid intake and does not diagnose dehydration. The FDA's revised general wellness guidance, issued in January 2026, addresses noninvasive products that sense physiologic parameters directly, and HydroBand is written to sit inside it. We are careful about this wording everywhere, including in the app.
Bioimpedance tracks change in body water better than it measures an absolute amount, and clinical work uses electrodes placed hand to foot rather than around one finger. HydroBand reports movement against your own baseline for exactly that reason. A university validation study is budgeted for the first year and the results get published whichever way they land.
Patches from Nix and Gatorade read sweat chemistry well, but they are single use and only work while you are actively sweating. HydroBand runs on a ring you already wear, through the whole day, including the hours before a session when the deficit actually builds.
Yes. Rated to 100 metres, which covers showers, pools, saunas, and open water. The ring has no ports or openings at all. The charging case is not waterproof.
Because it is doing more. Bioimpedance and electrodermal sensing both cost power that a sleep-focused ring does not spend. Five to seven days is the honest number, and heavy training weeks land at the low end.
The ring stores two weeks of readings and runs a smaller model on its own hardware. If you drop below your threshold, the light band flashes red until you acknowledge it with a double-tap.
No. The score, the alerts, and your full history come with the ring. The subscription tier is sold to organisations, not to you.
A free sizing kit ships first with eight plastic rings. Wear one for a full day, since fingers swell, then send the kit back in the prepaid envelope. Fit matters more here than on a watch, because a loose ring breaks sensor contact.