No app install. No Play Store. No pairing. Open your phone’s browser, accept a certificate warning, and see live voltage readings with GPS coordinates — pushed over an encrypted WebSocket every 400ms. The path from Bluetooth to this point took 5 iterations, one afternoon, and an AI coding agent that tested every change on real hardware.
A complete Bluetooth voltage monitoring system — ESP32 reads voltage via ADS1115 ADC, broadcasts over BLE GATT, and an Android app displays live readings in real time. Built end-to-end in ~6 hours across 3 platforms.
The goal: measure voltage wirelessly and display it on your phone. Simple enough, but it means touching embedded C++, Bluetooth protocols, and Android Kotlin — all in one session. Here’s how the 6 hours broke down and what we learned along the way.
My new project consists of HW with cost under 20€. It is able to accurately measure electric power consumption and sends data via WiFi. Great source of knowledge is openenergymonitor.org which includes also Arduino library.
I successfully run DHT22 battery ESP8266 temperature/humidity IoT sensor so my next project is a simple IoT Door Sensor. It is up and running and sending a simple event to my HTTP server via wifi chip ESP8266 (ESP-01 in my case). HTTP server is serving simple php script, that stores the data locally and also sending events to DWEET.IO and also sending email via Amazon SNS (AWS CLI api).
You can find several breadboard adapters for ESP8266 WiFi module or nRF24L01+ RF transceiver and also several DIY manuals how to create your own, but I decided to use my new WiFi WSP8266 and NRD24L01 as soon as I got them, so I used only breadboards female headers to start my home projects.
Check my my first IoT ESP8266 temperature humidity sensor project and my own ESP8266 ESp-01 programmer board.