27 kg
of load on your neck at a 60° phone-glance
Hansraj 2014 — a modelled estimate, not a direct measurement.
Posture, gently · for iPhone
Sit tall,
without thinking
about it.
Plumb is a calm posture companion for your desk and your AirPods. It quietly notices when you drift forward and nudges you back — gently, privately, all on your device.
A day with Plumb
Sit tall, without thinking about it. That’s the whole idea.
The quiet problem
Your body keeps a tally of every hour you spend leaning in.
A 60° glance is fine. A “pretty-good” angle held for forty minutes is a load history your tissues remember. Plumb is built around one honest idea: duration matters more than the perfect angle.
200%+
of standing disc pressure when you slump forward
Nachemson; replicated by Wilke 1999. Upright sitting alone is ~140%.
10– 20 min
before held tissue begins to creep and lose stiffness
Solomonow — recovery then takes hours, not minutes.
Plumb doesn’t measure pressure — no app can. It watches the postures that add it, and gives you a gentle prompt before duration adds up.
Two ways to sit well
One calm idea, however you work.
Both modes measure the same thing — how far your head has eased from the neutral you set. Pick whichever fits the moment.
Main mode · Free
Hands-free, with your AirPods
Your AirPods report head attitude about 25 times a second. Pocket the phone, lock it, switch apps. Plumb keeps tracking and cues you with a soft tone the moment you drift past your threshold.
- Phone away — works from your pocket
- Gentle audio cue through your AirPods
- A Lock Screen glance, with Plumb+
Desk alternative · Free
Camera, at your desk
Prop the phone in front of you. The TrueDepth camera reads your head and neck in real depth — never a saved photo or video — and a living figure mirrors how you’re sitting right now.
- Depth sensing, fully on-device
- No photo or video ever leaves the phone
- A living figure that mirrors how you sit
The living figure
A figure that mirrors how you sit.
While a check runs, a small figure sits exactly how you’re sitting — it tilts as your chin drops and warms when you’ve held a slump. One glance and you know which way to ease.
Two real moments, side by side: holding tall, then easing forward — the same figure, warming as your head drops.
Gentle by design
A nudge you’ll actually welcome.
Slip past your own threshold and Plumb lets you know — a soft tone in your AirPods, a tap, or both. It gets a touch more insistent on a long slump and stops the moment you ease back. Small movements and breathing inside a gentle neutral zone never count.
On your Lock Screen & Dynamic Island, with Plumb+
The Plumbline figure, a coaching word and your elapsed time — with a Stop button right there the moment you’re done.
- Your choice of cue — haptic, audio, or both, adjustable any time.
- Quiet by default — breathing and small shifts don’t trip it.
- Stops when you do — ease back and the nudge fades.
Progress, honestly
“Am I improving?” — answered honestly.
Your 0–100 score lives here. Insights leads with a big average and an honest, signed change — shown the moment there’s enough history to be fair about it. A true scale, and a trend you can trust.
- Always 0–100. A true scale, so a small wobble stays a small wobble.
- One mark per day. Quiet days stay as space, not guesses.
- Rewards time in neutral, not a lucky peak you touched once.
Grounded, not gimmicky
Built on the evidence — limitations and all.
Plumb ships a small Learn library on the biomechanics behind posture awareness, each source with its caveats stated plainly. They explain why noticing matters — they aren’t claims about Plumb itself.
-
Evidence
What Nachemson actually measured
Intradiscal pressure, sitting versus standing.
The catch 1960s in-vivo work, replicated by Wilke in 1999. The curve holds; the exact numbers carry uncertainty.
-
Evidence
Tech neck: the 60° myth and the real numbers
How neck load climbs as the head tilts forward.
The catch Hansraj 2014 is a mathematical model, not a direct measurement. We say so.
-
Technique
Why duration beats the angle
The creep phenomenon in viscoelastic tissue.
The catch Lab-instrumented spines; the direction translates, not a personal threshold.
-
Technique
The McKenzie extension principle
Disc-friendly movement, explained simply.
The catch A physiotherapy method delivered by clinicians. Plumb is awareness, not treatment.
-
Clinic
The plumb line
How physios read posture against gravity.
The catch A reference for awareness, not a standard you must hit.
All six reads live in full inside the app — short, honest, free to browse, no sign-up.
Get PlumbPrivacy isn’t a setting
Your posture never leaves your phone.
Plumb was built on a simple stance: the most private thing about you — how you sit, breathe and move — shouldn’t be anyone else’s data. So it isn’t. There are no servers, because there’s nothing to send.
Analysed on your device
Camera frames and AirPods motion are processed in the moment and discarded — never saved, never shown back, never uploaded.
No account, ever
No sign-up, no email, no login. There’s nothing to create and nothing to leak.
No ads, no trackers
No analytics, no data brokers, no third-party SDKs. Plumb’s Privacy Manifest declares zero tracking and zero data collection.
iCloud sync is off by default
Turn it on if you want a backup — and it goes only to your own private iCloud, never a Plumb server. (Plumb has none.)
Health is write-only
Plumb can log a Mindful Minute to Apple Health. It never reads anything from your Health data.
Erase in one tap
Clear your whole session history whenever you like, straight from Settings.
Protected by iOS’s built-in, device-level encryption. No special claims — just Apple’s defaults, kept local.
Read the full Privacy PolicyWhat Plumb doesn’t do.
The fastest way to lose your trust would be to overclaim. So here’s the plain version — the same caveats live inside the app.
It’s not a medical device
Plumb builds posture awareness — it doesn’t diagnose, treat, or monitor any condition. For pain, numbness, or anything that worries you, see a clinician.
It can’t see your lower back
A front camera and AirPods read the head, neck and upper spine. The lumbar curve sits behind you. That’s honest hardware reality, and a future direction, not a judgement.
Camera mode is head-first
At a desk, the front lens reliably reads your head and a little of your upper spine. We show exactly that — a friendly figure, not a full-body scan.
It learns your neutral, not an ideal
Plumb doesn’t impose a textbook posture. You set your own comfortable tall at the start, and a check simply notices when you’ve eased away from it.
Simple pricing
Start free. Go premium when it clicks.
Both modes — hands-free and camera — and a daily check-in are free, forever. Plumb+ adds unlimited, any-length checks, the hands-free Live Activity, full month & year Insights, and CSV/PDF export.
Free
£0 always
Everything you need to start noticing.
- Hands-free & camera modes
- One check-in a day (5 min)
- Two weeks of Insights
- Full pain log + the Learn library
Weekly
£3.99 per week
Try premium, no commitment.
- Lock Screen & Dynamic Island
- Unlimited, any-length check-ins
- Open & timed sessions
- Full Insights — month & year
- CSV & PDF export
Annual
£39.99 per year
The best value — under £0.77 a week.
- Lock Screen & Dynamic Island
- Unlimited, any-length check-ins
- Open & timed sessions
- Full Insights — month & year
- CSV & PDF export
Lifetime
£79.99 once
Pay once. Yours for good.
- Lock Screen & Dynamic Island
- Unlimited, any-length check-ins
- Open & timed sessions
- Full Insights — month & year
- CSV & PDF export
Billing is handled securely by Apple through the App Store — no card details are ever stored on your device. The 7-day trial is on the Annual plan; trial eligibility is set by Apple. Cancel anytime in App Store → Subscriptions. Prices shown in GBP.
Questions people ask first
Do I need AirPods to use Plumb?
No. Both modes are free. Hands-free uses the motion sensors in compatible AirPods or Beats — it’s the main everyday mode — and camera mode works at your desk with just your iPhone.
Is my data really private?
Yes. Everything is analysed on your device — there are no Plumb servers, no account, no analytics and no trackers. Camera frames and AirPods motion are processed in the moment and discarded; only your scores and session summaries are saved, locally. iCloud sync is off by default and, if you turn it on, goes only to your own private iCloud .
Is Plumb a medical device?
No. Plumb is a wellness and posture-awareness tool. It doesn’t diagnose, treat, or monitor any medical condition. If you have pain, numbness, or anything that concerns you, please see a qualified clinician.
Does it track my lower back?
No — and we won’t pretend otherwise. A front-facing camera and AirPods can see your head, neck and upper spine. The lower back sits behind you; that’s a hardware gap we’re honest about, and a future direction for Plumb.
Which AirPods are compatible?
Motion-capable AirPods and Beats — for example AirPods Pro, AirPods (3rd generation), AirPods Max and Beats Fit Pro. Apple determines the exact set at runtime, so Plumb simply checks whether your headphones report motion.
Can I use it with the phone in my pocket?
Yes — that’s the point of hands-free mode. Plumb keeps tracking with your phone locked or in another app, and nudges you with a quiet tone through your AirPods. Plumb+ adds a glanceable Live Activity on your Lock Screen and Dynamic Island.
Is there a free version?
Yes, free forever: both modes, one check-in a day, your Today view, the full pain log, two-week Insights and the whole Learn library. Plumb+ adds unlimited check-ins of any length, the hands-free Live Activity, full month/year Insights, and CSV/PDF export.
Is Plumb available now?
Yes — Plumb is on the App Store. It’s free to start, with a gentle check every day; Plumb+ unlocks unlimited and longer checks, hands-free Live Activity, and more.
It’s here
Sit a little taller, today.
Plumb is on the App Store — a calm, private nudge for your desk and your AirPods. Free to start, with a gentle check every day.
On-device. No account. Free to try.