Effective date: 28 April 2026 · Last updated: 21 September 2026
SIS is a pattern-tracking and summary tool designed to help individuals record symptoms, appointments, and health-related information in a calm, non-diagnostic way. SIS is published by TI BARJAC LTD, a company registered in the Republic of Cyprus under number HE 476931, with its registered office at Onisiforou Center, 2nd floor, Neofytou Nikolaidi & Theodorou Kolokotroni, Agios Theodoros, 8011 Paphos, Cyprus. "We", "our" and "us" mean TI BARJAC LTD, which is the data controller for the limited personal data this policy describes.
Your privacy is foundational to how SIS is built. This policy explains, plainly and fully, how your information is handled when you use SIS.
SIS allows you to enter personal health-related information, including:
Family history. SIS also lets you record conditions that run in your family — a relative's relationship to you, which side of the family they are on, what was diagnosed and at what age. This is health information about other people, so it is recorded carefully: SIS stores the relationship only, never a name, and there is nowhere in the app to type one. It is kept on your device with the rest of your record and it is removed with it.
This information is entered voluntarily by you and is stored only on your device. Your record lives under womens-health-pattern-app, your diary entries under sis-diary-entries, and anything you add to Documents under womens-health-documents. Voice notes you record are kept as audio files on your device, listed under sis-voice-recordings. So that your record survives if your phone clears the app's web storage, SIS also keeps a second copy of these on the same device, in the app's own storage, under keys beginning sis-durable:. If your record has ever moved between versions of the app, SIS may also still hold a complete copy of it under the older key it used then, kept so that an upgrade can never be the thing that loses your record. Alongside those, SIS keeps a handful of small settings keys beginning sis- — things like whether you have seen a particular notice, the name you gave your summary, and whether you have turned Big Sis on. None of the settings keys contain health information, and none of this leaves your device.
We never receive this information and we have no access to it. Nothing you enter is transmitted anywhere, other than the optional Big Sis feature, which sends only what you choose — see section 6. There are copies of it, and they are all on your phone: the second copy described above, plus any backup file you choose to save. If you delete the app, or clear its data in your phone's settings, what is on the phone is gone — including from us, because we never had it. Clearing only the app's web storage is not enough on its own: the second copy is what brings your record back after that. The one action that removes everything is Delete all my data inside the app. A backup file you saved somewhere else is yours alone — only you can delete that.
SIS does not use analytics. There is no analytics service in the app or on our website, no cookies, and no tracking of any kind. If that ever changes, this policy will be updated to say exactly what is collected before the change goes live.
If you contact us at hello@bigsis.health, we will see your email address and the contents of your message. We use this only to reply to you. We do not add you to any mailing list, and we do not share your email with anyone.
The hello@bigsis.health address is forwarded to a personal inbox managed by the founder. Email is not encrypted end-to-end — please don't include sensitive medical details in messages to us.
We do not:
The optional Big Sis feature is the one exception: when you use it, the information you choose is sent to an AI provider, acting on your instruction, to generate your reply (see section 6). This is a processing service you actively choose to use — not selling, advertising, or sharing your data for anyone else's purposes, which we never do.
Anything you choose to export from SIS (for example, a summary to share with a clinician) is entirely under your control. Once you export it, it leaves the protection of your device — please handle exports as you would any other personal medical document.
Big Sis is an optional, premium feature. Everything above about your health information staying on your device remains true — Big Sis is the single, deliberate exception, and it only ever operates when you choose to use it.
What it does. Big Sis helps you understand a term from your records, prepare questions for an appointment, or organise your journey into a readable summary. To do this it uses an external artificial-intelligence service — currently Claude, made by Anthropic — to generate a reply.
It is opt-in, twice over. Big Sis does nothing unless you turn it on (a one-time consent) and then confirm each individual send. Nothing is sent automatically or in the background.
What is sent — and what is not. Only the specific information you choose for that request is sent. Before anything leaves your device, we automatically remove things like email addresses, phone numbers, NHS numbers, postcodes and dates of birth written as numbers. Names are different. Removing them could change the words you used to describe what’s happening, so instead we show you exactly what will be sent first. You can edit any part of it, and if your own name appears, we’ll flag that for you. We send the minimum needed for the task, never your whole record, and in a continuing conversation only your new message plus the conversation so far. You also see roughly how much, before you confirm.
How it is sent. Your chosen information travels over an encrypted connection to a relay we operate (at ai.bigsis.health) whose only job is to pass the request to the AI provider and return the reply. It stores nothing, keeps no database, and does not log your health content.
Checking your subscription. Big Sis is a paid feature, so each request also carries a random ID that our subscription service, RevenueCat, gave this copy of the app. It contains no name, email or health information. The relay uses it only to ask RevenueCat whether your subscription is active, and never passes it to the AI provider or keeps it. If you were given a tester code, the app sends that code instead. RevenueCat handles subscriptions for us but never receives any of your health information.
The AI provider. The provider (currently Anthropic) processes your request to generate the reply. Under their commercial API terms they do not use the data to train their models and do not retain it after responding.
International transfer. The provider may process your request outside the UK/EU (for example, in the United States). This applies only to the information you choose to send, and is governed by the provider's data-processing terms and appropriate safeguards.
It still never diagnoses. Big Sis will not tell you what condition you have or interpret your results — it helps you understand and prepare, and routes decisions back to your healthcare team. It is not a medical device.
Your control. You can choose not to use Big Sis at all, use it for only some things, or stop at any time. A conversation is held only in memory while it is open, and is not saved anywhere once you close it.
SIS's long-term mission includes the possibility of feeding anonymous, aggregated patterns — never personal information — back into clinical and research systems, so that the experience of being dismissed becomes harder to repeat.
This is a future feature, not a current one. If and when it is built, it will:
Until then, other than the optional Big Sis feature described in section 6, none of your data leaves your device.
SIS is not a medical device. It does not diagnose, treat, monitor, or make clinical decisions. It is a personal record-keeping and pattern-noticing tool. SIS does not provide medical advice, diagnosis, or treatment, and is not a substitute for advice from a qualified healthcare professional. Always consult your doctor about any medical concerns. Big Sis, the optional AI companion, likewise does not diagnose or give medical advice; it helps you understand and prepare, and points decisions back to your healthcare team.
Because your information is stored only on your device, the security of that information depends on the security of your device and browser. We recommend:
SIS itself is delivered over HTTPS and does not transmit your health information anywhere — except where you actively use Big Sis (see section 6), which sends only the information you choose, over an encrypted connection.
Because we don't hold your personal health data, most data-protection rights (access, correction, deletion, portability) are exercised directly by you on your own device — your data is yours, immediately and completely.
For the limited information we do process (analytics and any email correspondence), and for the information you choose to send when you use Big Sis, under EU GDPR, UK GDPR, and equivalent laws in other regions, you have the right to:
To exercise any of these rights, email hello@bigsis.health.
SIS is available globally. Email sent to hello@bigsis.health is forwarded to an inbox managed by the founder in Cyprus. Because your health data never leaves your device, there are no international transfers of your health information — with one exception: if you use the optional Big Sis feature, the information you choose may be processed by an AI provider outside the UK/EU (see section 6).
SIS is intended for adults. It is not directed at children. Different countries set the minimum age for digital consent differently (commonly between 13 and 16). If you are under the age of digital consent in your country, please use SIS only with the involvement of a parent or guardian. If you believe a child has used SIS on a device you control and you wish to remove the data, clearing the browser's storage for the SIS site will delete it.
If we make material changes to this policy — for example, adding a new feature that involves processing data differently — we will update this page and revise the "Last updated" date at the top. For significant changes, we will surface a notice in the app itself.
For any privacy questions, requests, or concerns, please email:
SIS is built on the belief that your story belongs to you. This policy is the practical expression of that belief.