OpenTara

Open-source smart scale companion.

Local, private iOS app for Bluetooth body composition scales — no vendor account, no cloud.

OpenTara reads Bluetooth body scales directly on your iPhone and computes the full set of body metrics locally. All data stays on your device. It exists because the excellent openScale is Android‑only, leaving iPhone users with cloud‑bound vendor apps as the only option.

⚕️ Not a medical device. All values are estimates for personal orientation only.

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Features

• Read supported scales over BLE — passively (advertisement) or via connection (GATT)
• Body metrics with the original Xiaomi/Huami formulas (match Zepp Life / Mi Fit): weight, BMI + WHO class, body fat, water, muscle mass, bone mass, visceral fat, BMR, metabolic age, protein, lean body mass, body type, body score, ideal weight
• Waist/hip/chest/thigh/biceps/neck circumferences + WHtR/WHR, comments
• History with chart (weight / BMI / body fat), edit & delete, manual entry
• Multiple profiles with automatic assignment by weight (asks when ambiguous)
• Goal ring + projection ("reach your goal around …")
• Assisted weighing (babies / pets)
• Daily weigh‑in reminder
• Statistics, colour‑coded assessment, kg / lb / st units, show/hide metrics
• CSV import/export, PDF report (for your doctor)
• Fully offline, no account, no tracking

Supported scales

See SUPPORTED_SCALES.md for the live list and status.

Scale	Type	Status
Xiaomi Mi Body Composition Scale 2 (MIBFS)	advertisement	✅ verified on hardware
Xiaomi Mi Smart Scale v1 (weight only)	advertisement	🧪 experimental
Bluetooth‑SIG standard scales (0x181D / 0x181B)	connection	🧪 experimental

Have a Bluetooth scale? We need you. Most drivers are ported from openScale but not yet verified on real hardware. Helping is easy — see CONTRIBUTING.md ("Test or add your scale").

Install on iPhone (SideStore / AltStore)

Add this source URL in SideStore or AltStore — then OpenTara installs and updates automatically (no manual .ipa transfer):

https://raw.githubusercontent.com/etlami/opentara/main/source.json

SideStore signs the app with your own Apple ID, so it doesn't expire every 7 days. Alternatively grab the .ipa from Releases or build from source.

Requirements

• iPhone (a real device — the Simulator has no Bluetooth)
• Xcode (macOS)
• An Apple ID for signing (free works; app expires after 7 days — a paid Apple Developer account removes that limit)

Build & run

git clone https://github.com/etlami/opentara.git
cd opentara
open OpenScaleIOS.xcodeproj

In Xcode: select your Apple ID team under Signing & Capabilities, pick your iPhone as the run destination, and press ▶. On first launch, trust the developer certificate under Settings → General → VPN & Device Management on the iPhone.

The Bluetooth usage description (NSBluetoothAlwaysUsageDescription) must be present in the target's Info settings.

How it works

• ScaleDriver — protocol every scale implements; ScaleDriverRegistry lists them
• .advertisement drivers parse passive BLE broadcasts (e.g. Xiaomi)
• .connection drivers connect and subscribe to GATT characteristics (e.g. SIG scales)
• ScaleManager — scans, routes packets to drivers, handles connections
• BodyMetrics / BodyMetricsExtra — the body‑composition formulas
• Raw BLE bytes are logged in‑app to make calibrating new scales easy

Adding a scale = one new ScaleDriver in a file. See CONTRIBUTING.md.

Localization

The app is being localized via a String Catalog. See LOCALIZATION.md for status and how to add a language.

Privacy

No account, no network calls, no analytics. Everything is stored locally on the device. See PRIVACY.md.

Support

OpenTara is free and open source. If it's useful to you, you can support development:

☕ Buy me a coffee

Credits & license

• Formulas & BLE protocols ported from openScale and bodymiscale (both GPLv3).
• Licensed under GPL‑3.0‑or‑later — see LICENSE and CREDITS.md.

This project is not affiliated with openScale, bodymiscale, or Xiaomi.