Android · Open Source · GPL-3.0

Your phone is the hub.
Cheap boards are the ears.

A passive, camera-free perimeter tripwire. ESP32-S3 sensor nodes listen for Bluetooth signals and feed your phone over Wi-Fi — no cloud, no account, no AI. Everything runs on-device.

Features

Presence detection without cameras or cloud

BLE Tripwire turns inexpensive ESP32-S3 boards into passive BLE listeners, feeding real-time data to an on-device pipeline that runs entirely on your Android phone.

Passive BLE Listening

Sensor nodes silently observe Bluetooth Low Energy advertisements — phones, wearables, trackers — without transmitting scan requests or connecting to observed devices.

On-Device Processing

An embedded Node.js pipeline on your phone anonymizes, analyzes, and runs a deterministic zone-breach state machine. Nothing leaves the device.

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HMAC Anonymization

Device addresses are HMAC-anonymized at ingest with a per-install random key. IDs are not comparable across installs and not derivable from source.

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Tamper-Evident Audit Log

Every alert transition is written to an HMAC-chained audit log. Verify integrity anytime via the dashboard or API.

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No Cloud Required

Your phone's Wi-Fi hotspot is the only network. No accounts, no subscriptions, no outbound traffic. Total data sovereignty.

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Cheap Hardware

ESP32-S3 boards are inexpensive and widely available. Firmware is included as Arduino sketches — flash, configure your hotspot SSID, and go.

Get an ESP32-S3 on Amazon →

How It Works

A deterministic state machine for zone breach detection

Unknown emitters near a sensor trigger WATCH. Confirmed inside the RSSI threshold triggers ALERT. Rising signal strength across sweeps means someone is closing in.

WATCH

Unknown emitter detected near a sensor node

ALERT

Emitter confirmed inside the zone RSSI threshold

CLOSING

Signal strength trending up — highest priority

KNOWN

Baseline-captured devices in your environment



Architecture

ESP32-S3 node(s) ──(phone hotspot Wi-Fi)──► POST /api/sensors/ble-tripwire │ Node.js (nodejs-mobile, on-device) · HMAC anonymization (per-install key) · data-sufficiency gate · baseline compare · zone-breach state machine · HMAC-chained tamper-evident audit log │ WebView dashboard (localhost only)
Privacy Posture

Your data stays on your phone. Period.

BLE Tripwire was designed from the ground up with zero-trust, on-device privacy as a first-class requirement — not an afterthought.

Built for people who care about their perimeter.

Open source under GPL-3.0. Firmware, Android app, and server pipeline — all in one repo.

Explore the Repository