BLE & Bluetooth IoT

Bluetooth Low Energy is the sneakiest "free" protocol in 2026 — every $5 ESP32 is a BLE listener, and an army of cheap BLE sensors (thermometers, soil probes, motion, presence) just broadcast their state with no pairing required. The trick is getting those broadcasts to your hub.

For the hub above this layer see Smart Home Hubs; for the chip itself see MCU Platforms; for ESPHome firmware see IoT Firmware Platforms.

ESP32 Bluetooth Proxy — the breakthrough

• ★ ESPHome Bluetooth Proxy — flash an ESP32 with a tiny YAML config and it becomes a BLE relay for Home Assistant. Place ESP32s around the house; HA gets near-100% room coverage. The single best smart-home idea of 2024-2025; mature in 2026.
  • https://esphome.io/components/bluetooth_proxy.html
• Why it changed everything: USB BT dongles on the HA host see one corner of the house. Five $5 ESP32s scattered around see the whole house. HA aggregates RSSI for presence detection (mmWave-style).
• HA Voice PE doubles as a BT proxy — the official voice satellite is also a Bluetooth proxy when not actively voicing.

BTHome — the standard

• ★ BTHome v2 — open BLE telemetry standard from the HA team; vendor-neutral; firmware authors can publish "I am a temperature 21.3 C, humidity 45 %" over a standard BLE manufacturer-data layout, and HA auto-discovers them. The BLE answer to MQTT auto-discovery.
  • https://bthome.io
• Many cheap Xiaomi LYWSD03MMC thermometers can be reflashed to BTHome firmware (pvvx custom firmware) and become proper HA citizens.
• Shelly BLU sensors speak BTHome natively.

Theengs — the BLE decoder library

• ★ Theengs Decoder — C++ library that parses 2,000+ BLE devices from manufacturer data without pairing: Xiaomi LYWSD03MMC, Govee H5xxx hygrometers, Inkbird thermometers, Polar HR straps, Mi Flora plant sensors, Qingping monitors, and more.
  • https://github.com/theengs/decoder
• ★ Theengs Gateway — Python daemon that uses Theengs Decoder + a USB BT dongle and publishes everything to MQTT.
• Theengs is built into OpenMQTTGateway, so an ESP32 with OMG firmware does the same thing as the Pi-based Gateway.

Specific brands worth knowing

• ★ Govee — H5xxx series thermometers / hygrometers / leak sensors are cheap, ubiquitous, and read perfectly via Theengs / OMG / ESPHome BLE without Govee's cloud.
• ★ Xiaomi LYWSD03MMC / MJWSD05MMC — $4 BLE thermometer; reflash with pvvx ATC firmware → BTHome → HA.
• Mi Flora — plant moisture / fertility sensor; classic BLE; supported via Theengs / OMG.
• Inkbird — BBQ probes; well-supported.
• Switchbot — BLE bots and curtain controllers; need the Switchbot Hub 2 for cloud-free or talk directly via BT proxy.
• Tile / AirTag — proprietary BLE trackers; outside HA scope (Apple's FindMy is closed).

Presence with BLE

• iBeacon / Eddystone static beacons + ESP32 BT proxies → room-level presence.
• ★ ESPresense — ESP32 firmware specifically tuned for room-level BLE presence with RSSI calibration and trilateration. Pairs with HA. Lighter than running ESPHome BT proxies if presence is your only goal.
  • https://github.com/ESPresense/ESPresense
• See Presence & mmWave for non-BLE presence.

On-the-go / phone-side

• nRF Connect for Mobile (Nordic) — the BLE Swiss-army-knife app; scan, advertise, log; iOS + Android.
• Bluetility (macOS) — desktop BLE scanner.
• BlueZ (Linux) — bluetoothctl, gatttool, btmon. Low-level Linux BT.

Practical guidance

• ★ One ESP32 BT proxy per ~1500 sq ft / 150 m². Walls and metal furniture matter; more is better than fewer.
• USB BT dongles on the HA host are unreliable. Heat, USB 3 noise, and the kernel BT stack all conspire. Replace with ESP32 proxies.
• PoE-powered ESP32s in ceilings / closets: best long-term install.
• Don't pair to a BLE device casually — a bonded device only talks to one master, and your HA proxy can't read its broadcasts anymore. Theengs / pvvx firmware are passive listeners — never pair.

Pick this if…

• Default coverage: five ESPHome BT proxies around the house.
• Cheap BLE thermometer: Xiaomi LYWSD03MMC + pvvx firmware → BTHome.
• Pi-based BLE gateway with no flashing: Theengs Gateway + USB BT dongle.
• Room-level presence focus: ESPresense.
• All BLE + 433 + IR in one ESP32: OpenMQTTGateway (see IoT Firmware Platforms).