Open source tools for the Hilo (TM) (formerly Aktiia) BLE blood pressure cuff. Includes a Python desktop client and an Android holter app for unattended periodic measurements.

The cuff uses a proprietary BLE protocol — there is no standard Blood Pressure Service (0x1810).

1. Scan for devices advertising with name prefix "AKTIIA C"
2. Connect (the cuff automatically starts inflating upon BLE connection)
3. Subscribe to notifications on a6b40002
4. Wait for notification (the cuff takes ~45 seconds to measure)
5. Parse the 5-byte notification payload
6. Read the status byte from a6b40003
7. Disconnect

No authentication is required beyond standard BLE pairing.

The measurement notification is 5 bytes (only the first 4 are used):

The status byte read from a6b40003 after measurement:

Error types (when status != 2, value is in the diastolic byte):

The cuff has a physical power switch. As long as the switch is on, each BLE connection + notification subscription automatically triggers a new measurement without any user interaction. This enables holter-style periodic monitoring.

Desktop client using bleak for BLE.

cd python
python3 -m venv venv
source venv/bin/activate
pip install bleak

# Single measurement (verbose output)
python3 bplog.py

# Holter mode: repeated measurements every 300 seconds
python3 bplog.py --holter 300

Single mode prints full details (battery, raw bytes, parsed values). Holter mode prints one line per measurement:

Mar 5, 12:34:22 135/85 BPM 58
Mar 5, 12:39:48 130/82 BPM 55
Mar 5, 12:39:48 ERROR (status: 1)

Foreground service app that performs periodic BLE measurements in the background, stores results in a local database, and provides a share function.

Requires Android SDK command-line tools with platform 34 and build-tools, and JDK 17.

cd android
echo "sdk.dir=/path/to/android/sdk" > local.properties
export JAVA_HOME=/path/to/jdk17
./gradlew assembleDebug

The APK will be at android/app/build/outputs/apk/debug/app-debug.apk.

adb install -r app/build/outputs/apk/debug/app-debug.apk

• Set measurement interval in minutes
• Start/Stop holter monitoring via foreground service
• Persistent notification showing last reading and next measurement time
• Local Room database storage of all measurements
• Share measurements as text (format: Mar 5, 09:02:01 134/86 BPM 57)
• Supports Android 11+ (API 30+)

This project is an independent, open-source effort to interoperate with the Hilo (TM) blood pressure cuff. It does not infringe on Hilo's intellectual property:

• Reverse engineering for interoperability is a protected right. The EU Software Directive (2009/24/EC, Article 6) explicitly permits reversing to achieve interoperability. In the United States, courts have consistently upheld reverse engineering for interoperability under fair use (see Sega v. Accolade, 977 F.2d 1510; Sony v. Connectix, 203 F.3d 596; Oracle v. Google, 593 U.S. 1).
• No access controls are circumvented. The cuff requires no authentication — any BLE client can connect and receive measurements. There is no DRM, encryption, or technological protection measure involved, so the DMCA anti-circumvention provisions (17 U.S.C. § 1201) do not apply.
• No copyrighted code is redistributed. This project contains only original code.
• Communication protocols are not copyrightable expression. The BLE protocol is a functional specification (a 5-byte data format), not creative expression eligible for copyright protection.
• Users operate their own hardware. This software enables device owners to use their purchased hardware with the software of their choice.
• No trademarks are misused. "Hilo" and "Aktiia" are used solely for identification and compatibility purposes (nominative fair use). This project is not affiliated with, endorsed by, or sponsored by Hilo or Aktiia.

MIT