This cool ESP32‑S3 project is like a Geiger counter but for finding your phone instead of radiation

Credit: Stunning-Macaron1591 Published Sep 8, 2026, 11:50 PM EDT Simon is a Computer Science BSc graduate who has been writing about technology since 2014, and using Windows machines since 3.1. After working for an indie game studio and acting as the family's go-to technician for all computer issues, he found his passion for writing and decided to use his skill set to write about all things tech. Since beginning his writing career, he has written for many different publications such as WorldStart, Listverse, and MakeTechEasier. However, after finding his home at MakeUseOf in February 2019, he would eventually move on to its sister site, XDA, to bring the latest and greatest in Windows, Linux, and DIY electronics. Sign in to your XDA account Summary BLE Finder quietly guides you to your phone with Geiger-like clicks and vibrations instead of loud ringtones. Built with an ESP32-S3 (Arduino core), passive buzzer, and motor; scans BLE by MAC address and runs locally. On-screen proximity labels (same room/same table) help pinpoint location; full build details on GitHub. It's always a terrible feeling when you lose your phone, but you're in a quiet environment. Ringing your phone is the obvious answer, but then you blast everyone with your ringtone. But what if, instead of having your phone call out as loudly as possible, you instead had a device that quietly guided you to it? Such is this handy little device that sounds like a Geiger counter, but instead of detecting radiation, it locates your phone. The BLE Finder makes finding your phone a lot less loud It also sounds really cool Over on the ESP32 subreddit, user Stunning-Macaron1591 showed off the BLE Finder. It's a device that runs off the ESP32-S3, with an Arduino‑ESP32 core, a passive piezo buzzer, and a small vibration motor. Once built, you can pair it up with your phone and use it to locate it if it goes missing: "I made a pocket “find my phone” device on ESP32‑S3: it scans BLE around you, tracks your phone by MAC, and gives audio/haptic feedback — the closer you get, the faster the clicks, so you can just follow the sound/vibration instead of staring at a screen. Everything runs locally on the ESP32, no cloud or phone app needed." You can see and hear it in action in the video above. Other than the display showing a number and the Geiger-counter-like clicking, it looks like there's a brief estimate of where the device is. The little message at the bottom reads "same room," then changes to "same table" as the device approaches the phone. Seems like a very useful feature for getting a vague estimate of where the phone is. If you'd like to make your own, head over to the BLE Finder GitHub page for all the details.