Smart home automation is the ultimate life hack, in my humble opinion. Whether for efficiency, accessibility, nerding out, or just plain laziness, all you need are smart home devices and a little problem solving. In a lot of cases, the smart home tech you need above all is a sensor. As part of my goal to help you learn to build automations that make your lives easier, here's a compendium of what you can measure with smart sensors available on the market now.
For the purposes of this list, which I compiled with the help of Reddit, I'm only listing devices that are fully cooked, not DIY options like Raspberry Pi. 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. Every single sensor is different, so the capabilities of each one, even within a single category, may be different. Alarm Mat For Bed
What it measures: In most cases, these sensors are both a thermometer and hygrometer, so they'll measure the temperature and humidity. In some cases, like the Nest thermostat, they only measure temperature. Usually, these sensors can measure the ambient air around it, but in some cases, like the Meross Wifi Socket Thermostat, they have a probe.
Use cases: The most common use for a thermostat will be to run your home's HVAC system, but because these are smart, you can also use them to tell other heaters and coolers, like window A/C units, when to turn on and off. You can use a combination temperature and humidity monitor for a greenhouse, or to grow mushrooms indoors by turning on fans, heaters, and humidifiers. Use a sensor with a probe to control the temp and humidity in a beer fridge, cheese or charcuterie cave, or just to monitor an exterior fridge or freezer, receiving alerts if they go out of a set range.
Temperature/humidity sensors to consider:
meross Smart Temperature Controller Thermostat $54.99
What it measures: These sensors stay on the floor and alert when they detect wetness. If the sensor has a "dry" state, you can use that status as a trigger.
Use cases: Set a water leak sensor under your water heater, under sinks, and in corners that experience water intrusion during storms. You can also place them under fish tanks or aquariums, planters, or your washer/dryer, since their goal is simply to alert you to a leak.
Water leak sensors to consider:
Moen White Flo Smart Water Leak Detector $129.99
Aeotec SmarThings Water Leak Sensor $36.99
What it measures: These sensors have two parts: When your door or window is closed, the sensor's two parts connect, and when they're open, they disconnect. Technically, you could use them on anything where one state will align the two parts of the sensor and the other state will misalign them.
Use cases: These sensors are almost always part of a home security system, so they're used on exterior doors and windows. But consider using them as triggers for more passive things, like bathroom lights. When the door is shut, the light is on: When it's open, the lights go off. Since these are wireless sensors, you can use them on a weather-protected gate or a kid's playhouse.
Door/window sensors to consider:
SwitchBot Door Alarm Contact Sensor $24.99
Aqara Door and Window Sensor $24.99
What it measures: Using acceleration sensors, these wireless sensors can actually measure vibration, and usually, tilt and drop.
Use cases: Monitor your kitchen countertops for pet-related incursions, and ensure a delicate vase doesn't get moved. Add a vibration sensor to a backyard fence to check if a pet is trying to break out. Make sure your pet ate their food by attaching one to the underside of the food bowl. Place one in a space with items you don't want kids to get into.
What it measures: Any broad activity in a defined space. These sensors use infrared, radar, and sound waves to detect changes that mean someone or something is in the space.
Use cases: If someone passes into the hallway, turn on a light. If someone moves past a door, send an alert. If a pet enters a space, play a sound. If someone enters the garage after 8pm, send an alarm. Check for rodents in a basement or garage.
Eve Motion (Matter) — Smart Motion Sensor $39.96
What it measures: Unlike motion sensors, which detect movement to tell if someone is moving around in a space, a presence sensor can tell if someone is, well, present in the space. Imagine sitting and reading a book in your living room, or just sitting quietly at a table.
Use cases: The most obvious application is lighting, since the lights will stay on as long as presence is detected. But also, you can send an alert when there is no presence detected, meaning people have left the space. Turn on a robot vacuum when no one is in the space, but turn it off when there are. Turn on wifi when people are present in a business, but turn it off when they're not.
Linptech Wifi Human Presence Sensor $29.99
What it measures: Different sensors measure different elements, but generally, they measure particle pollution like PM2.5 and PM10, gases like ozone, sulfur dioxide, nitrogen dioxide, VOCs, and carbon dioxide to create an air quality index score. Most air quality sensors also measure temperature and humidity.
Use cases: You'd use these scores to trigger your air purifier, or turn it on to a higher level of cleaning. You could also use this to close smart windows and doors, or send an alert to your phone, flash lights in the house, or otherwise alert inhabitants to the air quality.
Air quality sensors to consider:
ecobee New Smart Thermostat with Air Quality Monitor $244.99
Kidde Smart Smoke Detector & Indoor Air Quality Monitor $71.49
Airthings 2960 View Plus — Battery Powered Radon & Air Quality Monitor $237.78
What it measures: While not recording specific sounds, these monitors measure decibels to detect how loud it is, and also how long it remained loud.
Use cases: These are mostly popular in short-term rentals to alert owners to loud visitors. However, noise sensors are also used in pet monitoring cameras, or could be purchased separately and used for that purpose. They can also alert to crying children. You could also consider an external sensor that monitors your party to ensure, on the record, you've never violated local noise ordinances. Same for construction.
What it measures: Simply: smoke. Since these usually come in the form of smoke detectors, they occasionally also monitor carbon monoxide. New sensors are capable of detecting smoke from cannabis and cigarettes, and smart smoke detectors can be smarter about detecting false alarms. (And they're certainly easier to turn off.)
Use cases: You'll use these as smoke detectors. However, since they're smart, you can add additional actions to follow an alarm, like locating the dog, unlocking all the doors for fire crews, or calling or sending an SMS to someone.
What it measures: These use infrared sensors that measure light in the air, because this is inversely proportional to the amount of CO2. As such, these sensors can give a fairly accurate measurement of CO2. They also might use electromagnetic energy to see how the air absorbs CO2, or they might measure electrical current to see how it reacts with CO2.
Use cases: If you have smart windows or doors that will open, doing so as a result of a CO2 alert would make sense. Otherwise, send alerts or make calls.
X-Sense Smart Smoke Detector Carbon Monoxide Detector $39.99
What it measures: This sensor measures luminance. Beyond just "off" (no light) and "on" (full light), these sensors can also detect brightness thresholds.
Use cases: Consider that you can use this to sense natural light, like the sun or the lights in your indoor space. Use it facing a window to sense when your curtains should open or close. Set an indoor light sensor to trigger doors to close, lock, and various other daytime tools to shut down. Imagine using a light sensor for agricultural purposes, in a greenhouse, or for ensuring your plants get enough light over a day.
What it measures: Unlike a water leak sensor, which just senses moisture, a water monitoring sensor is installed inline to your water line and monitors flow to try and detect leaks. Usually they have the capability to shut down the line if such a leak is detected.
Use cases: Traditionally, you'd use this in your home to simply detect leaks on any of your lines, but you can consider nontraditional uses like using them on an exterior dripline or sprinkler system, too. When such leaks are detected in either case, because these are smart, you can choose how alerts go out and who is alerted. An email to the plumber asking for an appointment could be automated, for example.
Water monitoring sensors to consider:
Moen 900-006 Flo Smart Water Monitor $499.98
Flume 2 Smart Home Water Monitor $249
What it measures: Like a water monitor, sensors are attached to your circuits monitor the energy consumption on that circuit. There are also entire circuit boxes that do this. If they detect any weird usage, they alert you.
Use cases: As with most monitors, the majority of automations will involve what notifications happen after the sensor is triggered.
Energy monitoring sensors to consider:
What it measures: Soil sensors see how much electric voltage soil permits through, since this is based on water content. This data is interpreted to tell the user how moist the soil actually is.
Use cases: Once you're using smart sprinklers and hose valves, you can use a soil sensor as a trigger to determine when or whether to water. This can also be true inside for a smart indoor watering system.
Soil moisture sensors to consider:
Ambient Weather WH31SM Soil Moisture Sensor $36.99
ZIGBEE Garden Soil Moisture & Temperature Meter $25.90
What it measures: Wind speed and direction are determined by ultrasonic transducers that measure the time between the moment a signal is sent and when it's received in two different directions. That time is affected by wind acceleration, and the comparison between the two helps determine wind direction.
Use cases: As with all other weather sensors, the agricultural uses are the most obvious. Even at home, high wind can mean an alert is sent to lower outdoor umbrellas, for example. With newer smart pergolas on the market, you may choose to open the roof in high wind events to reduce upward force.
Wind speed sensors to consider:
Netatmo Wireless Anemometer with Wind Speed and Direction Sensor $89.99
What it measures: The presence of rain. Many of us already have these on our car windshields. In most cases, sensors shoot infrared light and determine if water is present based on how much light is received back.
Use cases: Your home weather station, which likely includes a rain sensor, can be used as a trigger to not water that day; it can also be used to close outdoor blinds, close smart windows, or close an outdoor pergola.
ECOWITT WH40 Wireless Self-Emptying Rain Gauge Sensor $49.99
Davis® 0.01" Rain Gauge Smart Sensor $269
What it measures: Touch sensors are a fancy way of saying "button." These are just smart buttons, and you can use automation or apps to create actions as a result of the trigger (pressing the button).
Use cases: Buttons can do absolutely anything, and that's really the beauty of them. Use them as a blank slate for any set of actions you want. Buttons can also be stuck to the wall to imitate a wall switch.
SwitchBot Remote One Touch Button $19
Decora Smart Wi-Fi 4-Button Controller $24.99
What it measures: Sleep sensors work in a variety of ways, but most will monitor your breathing and heart rate and look for irregularities. A sleep tracking mat will track snoring, heart rate, and weight to alert to sleep cycle changes.
Use cases: Aside from tracking your own sleep cycle, you can also send alerts to other people if you live alone and are concerned. In broader use, monitoring babies or sick or frail adults are ideal use cases. Consider that a baby that wakes up can trigger a bottle heater elsewhere in the house, for example.
Amazfit Band 5 Activity Fitness Tracker $35.73
What it measures: These sensors simply measure the weight upon them, including when the weight is lessened. You'll see these in implementations like smart shelves.
Use cases: The reason Amazon invented these smart shelves was to make reordering smoother. Use one for drinks, and it'll automatically reorder them when enough weight is removed. However, you can abstract these to trigger alerts for when art is moved or touched, or when your dog comes to rest in their bed if the sensor is under it—any instance where weight is important.
Smart Caregiver Wireless and Cordless Weight Sensing Bed Pad $109.95
Smart Caregiver Chair Exit Alarm with Weight Sensing Pad $74.95
What it measures: Through a variety of modalities, both traditional (under the tongue or against the forehead) and modern (wearables like watches), these sensors can alert to any temperature outside the range of what is considered normal.
Use cases: Use as a DIY fertility tracker, trigger alerts for fevers, or use as triggers for A/C or heaters based on core temp.
Body temp sensors to consider:
Easy@Home Smart Basal Thermometer $39.99
What it measures: How much gas is oxidized by electrical current, which indicates concentration of gasses like propane or natural gas.
Use cases: When triggered, open smart windows, send alerts, unlock doors for the fire department and turn off any smart devices like stoves or ovens that use gas.
Gas leak sensors to consider:
Splenssy Gas Leak Alarm Household Smart Sensor $19.99
What it measures: A simple motion sensor that detects when the door of the mailbox is opened or closed.
Use cases: Send alerts that the mail has been received, or more creatively, consider activating the dog treat camera so your pet is distracted while the mail is being delivered.
What it measures: Measures vibrations and the sound of breaking glass to alert you to broken doors and windows.
Use cases: For businesses and cities with high car theft, these alarms can quickly alert you of any problems. Consider activating your alarms and all security cameras when they're triggered.
Glass break sensors to consider:
Ring Alarm Glass Break Sensor $39.99
Wifi Smart Window Glass Break Sensor $39.99
What it measures: These pool sensors tend to measure multiple things: temperature, pH, and chlorine.
Use cases: When paired with the growing ecosystem of smart pool vacuums, filters, water valves, and even chlorinators, you can create an almost autonomous pool system where triggers deploy actions across all your smart pool devices.
Pool temp/pH sensors to consider:
Sutro Pool & Spa Water Smart Monitoring Device $499.99
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