Android Fitbit Middleman

A Android application that received data from Fitbit companion and forward to main server hosted on pc.

Overview

This application acts as a middle-man connecting Fitbit and PC Main Server. It is built for major purposes below:

1. To received data from Fitbit companion on the SAME Android device (i.e. Google Pixel phone).

2. To forward the data received to pc main server.

3. The reason of having this application is due to the restriction that Fitbit companion can only do POST request to the same device (phone in our case), or a non-self-signed https url. Hence, this Android app helps to achieve the communication between Fitbit and PC server.

How to install

Option 1: debug apk file on GitHub

There is a release apk file on GitHub Repo. Download the apk file from the phone to install the app. You will need to allow the permission requested on device while downloading and installing. Note that the apk file is unsigned debug build, it is not meant for public, but it is a quick and easy solution for internal use.

Option 2: install using Android Studio

To install the application on the devices (phones), connect the phone to the computer that has this project opened in Android Studio. On the top right of Android Studio, select the devices connected, and click run app button (green triangle). After running the app, Android studio should install a dev version of the app in the phone. The app is called System Fitbit Connector on the device.

Configuration

Tip

Do a search of !!ChangeMe in MainActivity you can find all the variable that might need to be changed.

Tip

The app is designed to update the destination IP address automatically, fitbit-receiver is the server that updates the IP. In the occasion that it is not forwarding to the right IP, try closing the app (from running in the background) and restart the app.

1. The app will update/resolve the IP address using a serverless API hosted on vercel. If the IP address shown is not correct, click on the refresh button.
2. Each device's colour/role can be change on the text field in the app. Please make sure it is correct, the fitbit-receiver will record incoming data according to the role name.

How to run

After installation, find the app on the phone to open it. The application should start working once opened.

Local backup

The app has a local backup feature implemented. It will save the heart rate data in the app directory. The data will only be kept for 5 days (duration can be changed in the code). Follow the instruction below to access the backup data.

The app is writing backups to:

/sdcard/Android/data/com.example.systemfitbitconnector/files/backups/

(each day: incoming-YYYYMMDD.jsonl)

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For macOS

1) Install ADB

Option A (easiest):

brew install --cask android-platform-tools

Option B (manual): download Google’s “Platform-Tools” zip, unzip it, and use the platform-tools folder. (No driver needed on macOS.)

2) Enable USB debugging on the phone

• On the phone: Settings → About phone → Build number → tap 7 times to enable Developer options.
• Back to Settings → Developer options → USB debugging → turn ON.
• Connect the phone via USB, choose File Transfer mode if prompted.
• When the “Allow USB debugging?” prompt appears, tap Allow.

3) Verify ADB sees the device

adb devices

You should see your device listed as device (not unauthorized).

4) List your backup files (optional check)

adb shell ls -l /sdcard/Android/data/com.example.systemfitbitconnector/files/backups

5) Copy backups to your Mac

• Copy the whole folder:

mkdir -p ~/Desktop/fitbit-backups
adb pull /sdcard/Android/data/com.example.systemfitbitconnector/files/backups ~/Desktop/fitbit-backups

• Or copy a single day:

adb pull /sdcard/Android/data/com.example.systemfitbitconnector/files/backups/incoming-20250929.jsonl ~/Desktop/

Tip: /sdcard/ and /storage/emulated/0/ are equivalent. If one path fails, try the other:

adb pull /storage/emulated/0/Android/data/com.example.systemfitbitconnector/files/backups ~/Desktop/fitbit-backups

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For Windows

1) Install ADB

Option A (manual, official): download the Platform-Tools zip from Google, unzip to e.g. C:\platform-tools. Option B (package manager): in an Administrator PowerShell:

choco install adb -y

(If you used the manual zip, run commands from C:\platform-tools or add that folder to your PATH.)

2) USB driver & debugging

• Install your phone’s USB driver if Windows doesn’t recognize it (most devices work out of the box; some vendors need drivers).
• On the phone: enable Developer options and USB debugging (same steps as macOS).
• Connect via USB, choose File Transfer if asked, and Allow the debugging prompt.

3) Verify ADB sees the device

Open PowerShell (or Command Prompt) and run:

adb devices

Your device should show as device.

4) List your backup files (optional)

adb shell ls -l /sdcard/Android/data/com.example.systemfitbitconnector/files/backups

5) Copy backups to your PC

• Copy the whole folder:

mkdir $HOME\Desktop\fitbit-backups
adb pull /sdcard/Android/data/com.example.systemfitbitconnector/files/backups $HOME\Desktop\fitbit-backups

• Or copy a single file:

adb pull /sdcard/Android/data/com.example.systemfitbitconnector/files/backups/incoming-20250929.jsonl $HOME\Desktop\

If you get a path error, try the alternate prefix:

adb pull /storage/emulated/0/Android/data/com.example.systemfitbitconnector/files/backups %USERPROFILE%\Desktop\fitbit-backups

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Common issues

• Device shows “unauthorized” in adb devices: unplug/replug USB, unlock phone, accept the Allow USB debugging fingerprint dialog, then run adb devices again.

• Permission denied / file not found: confirm the exact path using:

  adb shell 'ls -l /sdcard/Android/data/com.example.systemfitbitconnector/files/backups'

• Nothing listed yet: make sure the app has actually received/backup’d some payloads (your code writes on each forward).

• MTP/Finder can’t see Android/data: that’s expected on modern Android; use ADB as shown above.

Support

The app is last maintained by Jay, as of October 2025, feel free to contact him if needed :))