Best Sensor

The Apollo Automation AIR-1 is a compact indoor air quality monitor built by a small US company specifically for the Home Assistant community. It ships running ESPHome, the open-source firmware platform, and measures the pollutants that actually matter indoors: particulate matter across several size bins, volatile organic compounds, temperature, and humidity from its core Sensirion sensor module, with optional add-ons including a dedicated CO2 sensor for configurations that include it. Plug it into USB-C power, add it to your Wi-Fi, and it appears in Home Assistant over the local ESPHome API with no app, no account, and no cloud anywhere in the loop.

The Athom Human Presence Sensor is a compact mmWave radar occupancy sensor that ships with ESPHome, the open-source firmware platform, preinstalled. Where a PIR motion sensor sees only movement and marks a room empty the moment you sit still, millimeter-wave radar detects micro-movements like breathing and typing, so lights stay on while you are actually present. The hardware pairs an ESP32-class Wi-Fi microcontroller with an LD2410-family radar module, the same combination behind most of the DIY presence-detection builds in the Home Assistant community, except here it arrives assembled, cased, and flashed, typically for around twenty dollars.

The Zooz ZEN55 800LR DC Signal Sensor solves a narrow but valuable problem: getting your hardwired smoke and carbon monoxide alarms onto your smart home without replacing them. It wires into the interconnect circuit that hardwired alarms already use to trigger one another, listens for the DC signal that alarms place on that wire, and translates it into distinct Z-Wave smoke and CO notifications that your hub can act on.

The SONOFF Zigbee 3.0 USB Dongle Plus, commonly known by its model name ZBDongle-P, is a USB Zigbee coordinator built around the Texas Instruments CC2652P radio chip with a +20 dBm power amplifier and an external SMA antenna. Plugged into a machine running Zigbee2MQTT or Home Assistant's ZHA integration, it becomes the brain of a fully local Zigbee network, pairing and controlling bulbs, sensors, switches, and plugs from hundreds of manufacturers without any proprietary hub, account, or cloud service involved.

The Aqara Door and Window Sensor P2 is a small Thread-based contact sensor that reports whether a door, window, drawer, or cabinet is open or closed. Unlike Aqara's older Zigbee sensors, the P2 speaks Matter over Thread natively, so it pairs directly with any Thread border router and Matter controller, an Apple TV 4K, HomePod, Home Assistant with a Thread radio, or a SmartThings hub, without ever touching an Aqara hub or the Aqara cloud. Pairing is a QR-code scan, and from that point everything runs on your local network.