Effective July 29, 2026 · Published by Backbone Services Ltda
Fast Signal is a personal fasting, training, and recovery tracker. It reads data from Apple Health, lets you log your day manually, and shows you trends over time. This page covers what the app specifically collects, why, and how you can see or remove it — for our general company privacy practices, see our main Privacy Policy.
With your permission, Fast Signal reads data from Apple Health, one category at a time, only for what you explicitly grant:
Weight, body fat, lean mass, active energy
Resting heart rate, HRV, cardio recovery, VO2 max
Duration and respiratory rate while asleep
Runs, walks, HIIT, and other logged sessions
Date of birth, biological sex, height
The individual samples Health gives us — every reading, every workout — never leave your device; they're cached locally so the app works offline and used to build the screens inside Fast Signal. The one exception is the weekly AI-generated insights feature, which sends a small set of already-averaged weekly numbers off-device — see "AI-generated insights" below for exactly what that includes.
Fast Signal never tracks your location in the background. When you tap to add or confirm a location on a logged day, that one-time coordinate is used to look up the day's weather and altitude through Apple WeatherKit, then stored with that log entry as context — nothing more.
Meals, fasting windows, keto and alcohol days, mood, illness notes, free-text events, and your goals are entered by you and stored the same way as everything else — locally and, if enabled, synced through your own iCloud account. Your free-text notes are also read by the AI-generated insights feature described below.
Once a week, Fast Signal builds a short written summary of how your week went. Building it requires sending a limited, purpose-built set of data off your device — here's exactly what that is and isn't:
This week's and last week's already-averaged stats (e.g. average resting heart rate, not individual readings), workout and habit counts, your active goals, your age and biological sex, weekly-averaged weather and altitude for days you've logged a location, and your free-text notes for the week
Raw HealthKit samples, your date of birth, precise GPS coordinates, or anything from days outside the current week
You can turn off sending your free-text notes specifically, while keeping the rest of Insights, under Settings → Include notes in Insights.
That data is sent to a backend we operate (hosted on Cloudflare), which forwards it to Anthropic's Claude API to generate the written summary and immediately returns it to the app. Neither we nor Anthropic retain a copy — our backend doesn't store the data it processes, and the response comes straight back to your device, where it's saved locally like everything else. A generic identifier for your device (not linked to your name, Apple ID, or email) is used only to keep this feature from being spammed. Insights requires an active subscription (a 2-week free trial is offered first) — no data is sent off your device for this feature unless you're subscribed or trialing it.
If Fast Signal crashes, a technical report — device model, OS version, and the code path that failed — is sent to Sentry, our crash-reporting provider, so we can fix the bug. These reports don't include your health data, logs, or anything you've typed in.
Your logs, fasts, goals, and profile are stored on your device. If you have iCloud sync turned on, that same data is synced privately through your own iCloud account, encrypted in transit, into a private database only your Apple ID can read. The one thing we operate ourselves is the backend behind AI-generated insights, described above — it's a pass-through to Anthropic's API, not a database of your data.
Everything collected goes toward one thing: the trends, summaries, insights, and progress views inside the app. We don't sell data, run ads, or share it with data brokers. The outside parties involved are Apple's own frameworks (Health, Weather, iCloud), Sentry for crash reports, and — for AI-generated insights specifically — our own backend and Anthropic's Claude API. Never a marketing or analytics network.
Fast Signal isn't directed at children under 13, and we don't knowingly collect data from them.
If this policy changes in a way that matters, the effective date above will change with it.
Questions about this policy can be sent to jan.colson@backbonesvc.com.