How can you write (or have AI write) such an article without also sharing the code? Now it’s just a pretty useless brag, “look what I built”.

If you have a eufy scale, you can do this with no LLM needed - just set up an esp32 Bluetooth proxy, add it to home assistant, and then use the EufyLife integration someone already made. I did this recently with my scale to avoid having to sync it to my phone, go to the cloud, fetch data from the cloud, etc., and it's working fantastically. I have a little Home Assistant integration that pokes scale updates to a Python script running locally that provides a UI I like.

Huge fan of running it this way.

(Yesterday I ordered a more commercial, polished-looking esp32 Bluetooth proxy integrated into a smart plug - athome brand - but it's the same functionality, just in a nicer package than having a USB thing dangling from my outlet)

Is there any documentation and a specific esp32 Bluetooth proxy you would recommend?

esp32 bluetooth proxy: There's a standard esphome component that just turns any esp32 with appropriate h/w into a BTLE proxy: https://esphome.io/components/bluetooth_proxy/

I'm just using a cheap ESP-WROOM-32 but the recommended way to do it is with an wired ethernet-based ESP32 so you don't have interference with the wifi and btle. For a scale this works well enough. I haven't yet received the athom smart plug so I can't recommend it yet. Should be here in a week or so.

Once you've got the proxy you can just use the eufylife integration: https://www.home-assistant.io/integrations/eufylife_ble/

To setup the esphome bluetooth proxy you install esphome, and then create a yaml file that you'll use to configure the board, like this:

   esphome:
     name: bluetooth-proxy
   
   esp32:
     board: esp32dev
     framework:
       type: esp-idf
   
   # Enable logging
   logger:
   
   # Enable Home Assistant API
   api:
     encryption:
       key: "YOUR_KEY_HERE"
   
   # Enable OTA updates
   ota:
     - platform: esphome
   
   # WiFi configuration (matching the settings from your other devices)
   wifi:
     ssid: "YOUR_WIFI_SSID"
     password: "YOUR_WIFI_PASSWORD"
   
     # Enable fallback hotspot (captive portal) in case wifi connection fails
     ap:
       ssid: "Bluetooth Proxy Fallback"
       password: "proxyfallback"
   
   captive_portal:
   
   # Enable ESP32 BLE Tracker
   esp32_ble_tracker:
     scan_parameters:
       active: true
   
   # Enable Bluetooth Proxy
   bluetooth_proxy:
     active: true

Once that's done, plug in your board to your system and use esphome run bluetooth-proxy.yaml (you might have to find the device it's showing up as in tty.usbserial or whatever).

I'd love to be able to flash a custom firmware on the withings body+ to make the screen truly smart. It's a bummer to know that AI can do all these things if only the firmware was open source / accessible.

I've done it just by using their nice API, no need for any ESP32.

Withings has a full available API, I wrote a tool to just scrape what I need from the app at https://developer.withings.com/

Using AI to reverse engineer undocumented Bluetooth protocols has been a godsend for me. We have an RV that came with a "Smart RV" system from BMPro that controls all of the lights, the air conditioning, starting the generator, leveling, slideouts, and other stuff.

The BMPro app is... well, it's like they actively worked to make it terrible.

I put up with it for 2 years and then had the bright idea to throw the APK at Claude Opus earlier this year. I now no longer have to use their terrible app as it reverse engineered the Bluetooth protocol and I can either use the custom-built Android app, website hosted on GitHub Pages, or the Home Assistant app I built using AI.

It's not perfect, and it has bugs, but it is less buggy than their app. I've been busy at work lately, so I haven't had a chance to resolve the bugs, but I'll get around to it.

I ended up also using Opus to patch the original APK to fix several bugs and inexplicably bad UI choices they made. I still prefer to use my own app, but I have the patched app as a fallback.

Just to be pedantic, was it reverse engineered? Or did it just extract it out of the apk? Those are very different things imo

You can build your own scale with an ESP32 for like $25 in parts - Hx711, load cells, ESP32, and a handful of trivial components. I threw together one that sits under my gas bottle, so I know when it’s running low. Adding impedance would be a pretty trivial step.

Adding impedance would be a pretty trivial step.

But not the calibration that maps a raw ADC sample to "24.5% body fat, 21 Kg bone ..." etc.

Sure, you’ve gotta have some known good values to compare to, but those aren’t hard to come by. Pretty sure you can get a decent idea of BF with callipers or somesuch.