Therma privacy policy

Last updated: 12 October 2026

This policy describes Therma as it is built today, in beta. Therma is made by Chris Coughlan ("I", "me"). Contact: hello@productized.ltd.

Beta status: please read first

TestFlight builds of Therma currently sign in to one shared account, which is mine. Anything a build reads or records goes into that one account. The builds are for me, the developer, only. If you are not me, please do not install one until this page says per-person sign-in is in place.

What Therma reads from Apple Health

Only with your permission, which you give or refuse in Apple's own Health screen. On iPhone, Therma asks to read:

• Heart: heart rate, resting heart rate, heart rate variability, heartbeat series, one-minute heart rate recovery, walking heart rate average, VO2 max.
• Other readings: blood oxygen, respiratory rate, body temperature, sleeping wrist temperature, basal body temperature, blood pressure.
• Body measurements: weight, body fat percentage, lean body mass, height.
• Activity: steps, active and resting energy, walking, running and cycling distance, exercise minutes, stand minutes, flights climbed.
• Other: sleep, mindful minutes and workouts.

The Apple Watch app reads your heart rate during a sauna session, to show it live.

What Therma writes to Apple Health

The Apple Watch app saves each sauna round to Health as a workout, with its heart rate. The iPhone app asks for permission to save workouts but does not save anything to Health at present.

What is sent to the server, and why

Therma keeps your history in a database run on Supabase, a hosted database service, under the account the app is signed in to. The app's screens read from it, and journal entries are saved straight to it. This is what is sent:

• Daily summaries worked out on the phone from your Health readings, one row per day: for example heart rate variability, resting heart rate, sleep time and stages, steps, energy, body measurements and blood pressure, plus Therma's own daily scores and your 30 and 60 day baselines.
• Workouts: every workout in Health, not only saunas, with its times, type, duration, average and highest heart rate, energy, distance and source, and whether Therma thinks it was a sauna.
• Sauna rounds: average and highest heart rate, and a heart rate trace reduced to at most 60 points per round.
• Journal: what you write or dictate, including free text, mood and energy scores, tags and notes.
• Profile: your name, date of birth, sex, height, highest and resting heart rate, sleep need and chronotype, used to work out the scores.
• Things you log in the app: how a session felt, context tags such as alcohol, illness or caffeine, sauna goals, private experiments and any stress figures you enter.

Each row is tied to the signed-in account, and the database only lets an account read its own rows. I can also see the database directly, as its administrator.

TODO for Chris: confirm the Supabase project's region (the project notes say London, eu-west-2; not checked against the live project) and state it here.

TODO for Chris: state who is the data controller, the lawful basis for this health data under UK GDPR (Article 6 and an Article 9 condition, most likely explicit consent), and how consent is asked for in the app before anything is uploaded.

Sign-in

Today every build signs in automatically to the one shared account described above; there is no sign-in screen at launch. Sign in with Apple and email sign-in are built into the app but are not yet switched on.

TODO for Chris: rewrite this section when Sign in with Apple replaces the shared account.

What stays on your iPhone and watch

• Your individual Health samples. Therma reads them on the phone and sends only the daily summaries and sauna details listed above.
• Your voice. When you dictate a journal entry no recording is kept. Where your iPhone supports it, speech is turned into text on the phone; where it does not, Apple's speech recognition service is used. The resulting text is saved to the journal, and so to the server.
• A few settings and the sync position, in the app's own storage on the phone.
• The Apple Watch app never talks to the server. It saves workouts to Health and passes how a session felt to your iPhone.

What Therma does not do

No analytics, no advertising, no tracking and no third-party crash reporting. The app uses no third-party code apart from Supabase's own library for talking to the database.

If you take part in TestFlight, Apple shows me what it shows every developer, such as installs, crash reports and any feedback you choose to send. That comes from Apple, not from the app.

What the numbers are

Therma shows patterns in your own readings, compared with your own baselines. It describes associations, not causes. It is not a medical device, does not diagnose anything and does not give medical advice.

How long it is kept

There is no automatic deletion. Data on the server is kept until it is deleted (see below). Each sync rewrites the most recent 14 days.

TODO for Chris: set and state a retention period. The project also holds backup copies of daily summaries and workouts taken in August 2026 (backup tables from 24 and 30 August); decide whether to delete them and state it here.

Exporting your data

Therma has no export of your data today. Your Health data stays in the Health app, which has its own export.

TODO for Chris: add an in-app export, or say how to request one by email and how quickly you will answer.

Deleting your data

In Therma, open Settings, Data management, Reset everything, and type ERASE to confirm. It deletes your daily summaries, workouts, stress figures, journal entries, sauna check-ins and comparison log from the server, and resets the sauna streak counters to zero.

It does not delete everything. It keeps your profile (including your date of birth and sex), sauna goal targets and fixed baselines, and it also leaves your context tags, experiments, extra daily readings and sauna round heart rate traces on the server.

There is no account deletion in the app today. Signing out clears this device only; the account keeps all its data. To have everything deleted, email hello@productized.ltd.

Sauna workouts saved by the watch stay in Apple Health until you delete them there. You can stop Therma reading Health at any time in the Health app's settings for Therma.

TODO for Chris: make Reset everything (or a new Delete account) remove every row for the account, including the profile, and say here how long a deletion request by email takes.

Changes

If what Therma does with data changes, I will update this page and the date at the top.

Contact

Chris Coughlan, hello@productized.ltd.

In the UK you can also complain to the Information Commissioner's Office.