Smart home sensors: A guide to everything you need to know

Get a sense of what's out there and our pick of the best sensors

A guide to smart sensors
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If smart lights, thermostats and security cameras are the staples of the smart home, think of sensors as the invisible network meshing everything together. Or, if you prefer, the eyes of the smart home.

But the word sensor is itself pretty vague. There are many sensors out there designed to fulfill different purposes: movement sensors, light sensors, temperature sensors, and plenty more.

The best part about using sensors is that they’re (mostly) super easy to install, often with no wiring required, which will be music to the ears of renters. But before we dive into the specifics of each type of sensor and the best out there, let’s go over some need-to-know pointers.

Smart sensors: Things to know first

Many of the sensors you pick up today are wireless and battery-powered, allowing you to place them wherever you like. But the position of these sensors is key; if you have professional installing your smart home they should be able to provide some pointers – or just do it for you.

If you’re going DIY, think about the locations that are going to be most effective but least likely to cause false alarms if you're using them for security. Say you’re using a motion sensor, you’ll want to put it in a place an intruder is most likely to pass by, but not somewhere it might be triggered by daily visits from the next-door cat.

Read this: How to build a smart home when you rent

Sensors can also be used to connect your different smart home devices. If you have a hub-based smart home, using SmartThings, HomeKit or Alexa to tie everything together, sensors are another form of control, triggering routines and automations just by "sensing" your presence.

Here, you also need to think about compatibility. Are the sensors Z-Wave or Zigbee, Bluetooth or Wi-Fi? Do you want to buy the sensors as part of a bundle, which companies like Ring and Samsung offer, or are you better off buying the sensors individually?

Some smart home appliances also double as sensors of sorts. Smart doorbells have motion sensors in them and send you an alert when they see motion, and smart thermostats have temperature sensors in. Below, we've broken things down into the major categories of smart home sensors, and included some of our top picks.

Motion sensors

No points for guessing what these do. Motion sensors detect movement in a select area of your home, and can send you an alert, trigger a siren or turn other connected devices, such as lights, on or off based on motion or lack of it.

One thing to be aware of: You want to put motion sensors in a place someone is likely to pass by, not simply walk in front of. This will make it more accurate at detecting movement. There's no end of options out there for most every smart home ecosystem, whether your home runs on Zigbee, Z-Wave, HomeKit or Amazon Alexa.

Most motion sensors have an adjustable sensitivity. In researching motion sensors, you might come across something called PIR. This stands for passive infrared sensor, which detect warm bodies as they pass by. Other types of motion sensors include MW (Microwave), which bounces microwave pulses off objects; ultrasonic waves; vibration, which is a little less accurate and more prone to false positives; and sometimes a combination of more than one type.

Having an adjustable range can be hugely beneficial, depending on the space you're using it in. The key thing is to check the motion coverage and sensitivity before you buy, and whether the platform you're using it with will let you adjust those (Amazon Alexa doesn't allow sensitivity tweaking).

Some also come with a feature called 'pet immunity,' which is exactly what it sounds like. They shouldn't alert you if they detect movement from smaller beings in your home, and there's usually a maximum size noted (the Ecolink Z-Wave Plus Motion Detector claims immunity to movement from pets as large as 55 lbs, for example).

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Smart home sensors: A guide to everything you need to know

Samsung SmartThings Motion Sensor

$24.99, Amazon |

Samsung's Motion Sensor is a super handy device for placing anywhere in your home to detect motion and temperature, and trigger lights, alarms or smart home routines based on those. It's really small, so you can stick it to a wall or furniture and then use its magnetic mount to get the coverage you want. It works on the Zigbee protocol and you'll need either a SmartThings hub or Amazon Alexa Echo Plus or Show 2 to use it.

Smart home sensors: A guide to everything you need to know

Hue Motion Sensor

$39.99, Amazon |

If your concern is less about security and more about using motion to turn on the lights in your home - which, let's be honest, still feels amazing in 2019 - then Philips sells a Zigbee motion sensor for its Hue lights. It can even detect optimum daylight levels to conserve energy as needed.

If you have a Hue hub, you can connect this to a HomeKit setup, and it works with Alexa to trigger Routines (with a hub it works with any Alexa speaker, without you can pair it with an Echo Plus or Show 2). This means you can use motion, or the lack of it, to activate smart devices in your home other than just lights.

Smart home sensors: A guide to everything you need to know

Fibaro Motion Sensor

$69.99, Amazon |

Fibaro makes one of the best sensors for HomeKit users. There's a Z-Wave version too, so make sure you choose the right one. It's a little more expensive, but it's also better looking than most other motion sensors out there, if a little "Eye-of-Sauron". It also detects temperature and vibration.

Smart home sensors: A guide to everything you need to know

Onvis Motion Sensor

$25.99, Amazon

Another HomeKit option is Onvis. Inexpensive - which is not something you normally hear couple with HomeKit - this is a decent device for sticking in a room to trigger lights and it also has a temperature sensor.

Door/window contact sensors

Contact sensors are most often used as part of security systems, put on doors and windows to tell if they've been opened when they shouldn't have. But they're also really useful for knowing if anything has been opened or closed - blinds, fridges, drawers, garage doors, doggie doors, medicine cabinets, you name it. If it opens and closes you can stick a contact sensor on it.

You can use them as standalone devices, or pair them with a smart home system like SmartThings, Apple HomeKit or Amazon Alexa to do useful stuff such as have lights turn on, your alarm system disable, and maybe the TV turn on or the kettle start boiling when you open the front door.

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Smart home sensors: A guide to everything you need to know

Samsung SmartThings Multipurpose Sensor

$19.99, Amazon |

Samsung's Multipurpose Sensor is a three-in-one gadget - monitoring contact, temperature, and vibration. Really useful on doors - especially a front door as it can detect knocking - you can stick it anywhere two things connect. Also, thanks to the whole device being magnetic you can easily attach it to a metal gate, mailbox or door. It works with Samsung's SmartThings hub and Amazon Alexa's Echo Plus or Show 2.

Smart home sensors: A guide to everything you need to know

Stitch by Monoprice Wireless Smart Door/Window Sensor

$19.99, Amazon |

A Wi-Fi contact sensor, Stitch works with Alexa and Google Assistant, as well as its own app. No hub is required however, so you could just stick this on your front door and know when anyone opens it.

It's one of the few Wi-Fi sensors that works with Alexa Routines too, even without one of Amazon's Zigbee hubs, which is a great feature that lets you connect it to your other smart home stuff. Stitch also has a motion sensor.

Smart home sensors: A guide to everything you need to know

Eve Door and Window Contact Sensor

$39.95, Amazon |

The Eve Door and Window Contact Sensor is a HomeKit sensor that comes with extra spacers, so you can be sure the two parts of the sensor will be in correct alignment (key for non-standard doors and windows).

It uses BLE to communicate to a HomeKit hub (HomePod, Apple TV or iPad), but this means it can't be much more than 20 feet from the hub to work properly. Eve also has HomeKit compatible motion sensor, but neither will work with any other system.

Smart home sensors: A guide to everything you need to know

Moisture/water leak sensors

Handy, these, if you want to avoid coming home to a drenched house (or at least want a heads up). A lot of the traditional ones use alarms to alert you that something’s sprung a leak, but what if you’re not home to hear it blaring?

Moisture detectors can be placed in many places. Currently we have one on a washing machine that's outlived expectations and will likely fall apart soon, but heaters, bathtubs, and sinks are other obvious risk areas.

A key consideration is whether you want audible alerts as well as smartphone notifications. Not all of these sensors do both. Also, what type of notifications do you want? A text? A call? Think about that. And also consider what you already have in your home. Some of these sensors require a hub, but some can connect directly to Wi-Fi. If you want to connect your water sensors with other smart home devices – say, to switch off your lights if a leak is detected – then some will let you do so. And in some cases you can use IFTTT to build on the available options.

One of our top picks here is the iHome Wi-Fi Dual Leak Sensor (seen above), for which you can also set up triggers with iHome smart plugs to switch them off when a leak is detected. Samsung's SmartThings Water Leak Sensor works with the SmartThings hub and, in our testing, has proven to be pretty sensitive, even if it doesn't have quite as large a detection field.

Some water sensors also double as freeze detectors. The Roost Smart Water Leak and Freeze Detector, for example, or the less smart (but very capable) Honeywell Lyric Wi-Fi Water Leak and Freeze Detector.

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Smart home sensors: A guide to everything you need to know

iHome Wi-Fi Dual Leak Sensor

$29.99, Amazon |

The iHome leak sensor has dual probes for added coverage, and a battery life of two years. It's also loud as hell, with the option to push alerts to your smartphone - or integrate it with other iHome devices if you have them.

Smart home sensors: A guide to everything you need to know

Samsung SmartThings Water Leak Sensor

$19.99, Amazon |

Samsung's leak sensor doesn't have as much coverage as the iHome, but it's still easily one of the best options out there. It also monitors temperature, while SmartThings integration means you can tie it up with Alexa or Google Assistant.

Smart home sensors: A guide to everything you need to know

Temperature and humidity sensors

Temperature sensors are at their best when working in conjunction with smart thermostats. Sure, they can be helpful when they're alerting you that it's too hot or humid, but they're most effective in making your smart thermostat more efficient.

The best example here is the Ecobee's Room Sensors. Temperature sensors are great for effectively cooling or heating rooms. Let's say your thermostat is in your hallway and its 71 degrees Fahrenheit. In your room, it's 67 degrees Fahrenheit. Having a Room Sensor in that room will tell your HVAC that your room is colder than the hallway, and that it might need a little more heat.

Similarly, Ecobee's Room Sensors also check occupancy. So if they sense that someone is in a room, it'll heat it up, but if it's not then it won't waste the energy. This can make your heating system feel like it's following you around the house, which is super futuristic.

Temperature sensors can also be used to trigger other appliances. For instance, if it gets too warm maybe you can activate your fan. Or if it gets too cold you can activate your coffee machine. It's simple things like that that can end up making a world of a difference.

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Smart home sensors: A guide to everything you need to know

Ecobee Room Sensor

$79, Amazon |

You'll need an Ecobee Smart Thermostat, Ecobee4 or Ecobee3 Lite to use these, but the result is a much more intelligent way to heat your home. The sensors measure the temperature of individual rooms as well as where people are - so it can heat the home more efficiently.

Smart home sensors: A guide to everything you need to know

Monoprice Z-Wave sensor

$30, Amazon |

This one does it all: temperature, humidity, motion, and light. When the temperature changes by a specified amount, you'll get sent an alert - same with humidity. It's Z-Wave Plus, so you can use it as part of a Samsung SmartThings setup. Speaking of which, also consider Samsung's Multipurpose Sensor for temperature, which we mentioned earlier.

Smart home sensors: A guide to everything you need to know

Eve Room

$99.95, Amazon |

The second-gen Eve Room comes with a redesigned aluminum body and a high-contrast 1.54-inch E Ink display, which will tell you the temperature, humidity and air quality.

There are four different display layouts to choose from, and you can switch between them via touch panels on either side of the screen. The latest Eve Room has also done away with replaceable batteries in favor of a rechargeable one.

As with all Eve products this is only HomeKit compatible, but you can use it to set up HomeKit automations based on temperature changes - you need to use the Eve app to do this though.

Smart home sensors: A guide to everything you need to know

Netatmo Weather Station

$179.99, Amazon |

Designed as a weather station, Netatmo's indoor module monitors CO2, temperature, humidity and air quality, while the outdoor tower tracks barometric pressure, outdoor air quality and weather conditions, and like the indoor one, temperature and humidity. There's Alexa and IFTTT support - but not HomeKit

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