These tiny devices are smart-home helpers. They detect and alert you about motion, temperature, or open or closed doors and windows — and can tell other smart devices to act.

In the cases below, you can purchase a completed sensor and connect it to at least one major smart home hub: SmartThings, Google Home, Apple Homekit, Amazon Alexa or Home Assistant.

Different sensors detect activity such as motion, a door or window opening, and temperature, and then tell other devices how to react.

This weather-ready outdoor sensor from Philips Hue tracks motion, temperature and ambient light. It can trigger your lights and gadgets accordingly.

Espressif has many different types of ESP32 devices, and while "ESP32" is used as a general expression to refer to the line ...

There are absolutely motion sensors that are meant to work outside. Many smart home doorbells and security cameras have built-in motion sensors that can connect to your smart lights.

Aqara’s Presence Sensor FP2 is a huge step in smart home motion detection, and it means an even more efficient way to bring the home together without exactly breaking the bank.

The Hue Outdoor Sensor is the first outdoor HomeKit sensor, and adds motion, temperature, and light sensors to automate the outside of your Apple-centric smart home.

A better display and a temperature sensor accessory make Nest's Learning Thermostat more appealing.

Here’s how it works: Each Ecobee remote sensor appears twice in Apple’s new Home app on iOS 10, once as a temperature sensor and again as a motion detector.