Connected devices are physical objects embedded with sensors, software, and network connectivity that allow them to collect, send, and receive data. Your smartwatch tracking your heart rate, the thermostat you adjust from your phone, the doorbell that shows you who’s outside: these are all connected devices. The global count reached 18.5 billion in 2024 and is expected to hit 21.1 billion by the end of 2025, with projections pointing toward 39 billion by 2030.
The term overlaps heavily with “Internet of Things” (IoT) and “smart devices.” In practice, these labels describe the same idea: everyday objects that talk to each other and to the internet, performing tasks that once required manual effort.
How Connected Devices Work
Every connected device follows a basic pattern. A sensor gathers information from the physical world (temperature, motion, sound, light, location). Software on the device processes that data or passes it along. A network connection, whether Wi-Fi, Bluetooth, or a specialized low-power protocol, sends the data somewhere useful: your phone, a cloud server, or another device in the chain.
Some setups include a gateway, an intermediary device that collects data from multiple sensors and relays it to the cloud or a central app. A smart home hub is a common example. It sits between your individual light bulbs, locks, and cameras and the app you use to control them all. In industrial settings, a factory floor might have hundreds of sensors feeding data through a single gateway before anything reaches a server.
Where that data gets processed matters. Cloud processing means your device sends raw information to a remote server, which crunches the numbers and sends instructions back. This works fine for things like weekly fitness summaries, but it’s too slow for anything time-sensitive. Edge computing solves this by processing data right on the device or nearby, cutting out the round trip. A self-driving car can’t wait for a cloud server to decide whether to brake. The volume of data also plays a role: satellites in orbit, for instance, generate so much data that only the most relevant images get sent to ground-based servers. Everything else is processed on board.
Common Types in Everyday Life
Connected devices have spread into nearly every room and routine. The categories most people encounter first are smart home products and wearables.
- Home security: Outdoor cameras, video doorbells, smart locks, and full security systems that you can monitor from your phone. These range from professionally monitored setups to affordable DIY alternatives.
- Kitchen appliances: Smart ovens, refrigerators, air fryers, coffee makers, and robot vacuums. Many respond to voice commands or app controls, letting you start your coffee maker from bed or schedule a vacuum cycle while you’re at work.
- Climate control: Smart thermostats that learn your schedule and adjust heating and cooling automatically, plus connected air purifiers and fans.
- Wearables: Fitness trackers, smartwatches, heart rate monitors, smart scales, and medical alert systems. These sit on your body and continuously collect health data.
Beyond the home, connected devices power city infrastructure (traffic sensors, smart streetlights), agriculture (soil moisture monitors, automated irrigation), logistics (GPS-tracked shipping containers), and retail (inventory sensors, automated checkout).
Connected Devices in Healthcare
Healthcare has become one of the fastest-growing areas for connected devices, often grouped under the label “Internet of Medical Things.” Remote patient monitoring is the central use case: devices worn or placed in a patient’s home collect vital signs like heart rate, blood sugar, or blood oxygen and transmit the data to a care team without requiring an office visit.
Continuous glucose monitors, for example, give people with diabetes real-time blood sugar readings on their phone. Fall detection systems use sensor tags or wearable devices to identify when an elderly person has fallen and automatically alert caregivers. Some prototypes go further, using data patterns to predict falls before they happen. Body temperature and heart rate monitors can transmit readings to a patient’s phone via Bluetooth, triggering alerts when values move outside a safe range. These tools are particularly valuable for aging populations, where early detection of a medical emergency can be the difference between a minor event and a hospitalization.
How Devices Communicate
Not all connected devices use Wi-Fi. The protocol a device relies on depends on how much power it can afford to use, how far it needs to transmit, and how fast it needs to respond.
Wi-Fi is the most familiar option and handles high-bandwidth tasks like streaming video from a security camera. The newest standard, Wi-Fi 7, delivers speeds up to 30 gigabits per second (a massive jump from Wi-Fi 6E’s 2 Gbps) and supports significantly more devices on a single network with lower latency. This matters as households and businesses add more connected devices competing for bandwidth.
For devices that run on small batteries and don’t need to move much data, low-power protocols are more practical. Zigbee uses very little energy, making it well suited for sensors and smart lighting in a small home network. Thread is similarly low-power but optimized for fast response times, which is why it shows up in smart locks and speakers where a half-second delay feels noticeable. Matter is a newer standard designed to solve a persistent frustration: devices from different brands that won’t work together. It sits on top of Thread, Wi-Fi, or Ethernet and acts as a universal language so that a Google speaker, an Apple phone, and an Amazon plug can all control the same light bulb.
Security and Privacy Risks
Every device that connects to a network is a potential entry point for attackers, and many connected devices ship with weak security out of the box. Two problems are especially common. First, many devices come with default passwords that are easy to guess or publicly listed online. If you never change them, anyone who knows the default can access your device. Second, data transmitted between devices and servers is sometimes unencrypted, meaning someone intercepting the signal can read it in plain text.
These vulnerabilities scale. A single compromised smart plug is a minor nuisance, but attackers have historically hijacked thousands of poorly secured devices at once to form botnets, networks of infected devices used to overwhelm websites or services with traffic. The more connected devices on your network, the more important it becomes to change default credentials, keep firmware updated, and separate your IoT devices onto their own network segment so a compromised camera can’t give an attacker access to your laptop.
Where the Market Is Heading
The connected device market is growing at roughly 13% per year. IoT Analytics projects 39 billion connected devices globally by 2030, more than double the current count. Even at that pace, full market saturation isn’t expected before well after 2035, meaning the technology is still in a growth phase rather than a mature one.
Much of that growth is being driven by industrial and enterprise adoption (factories, supply chains, energy grids) rather than consumer gadgets alone. But the consumer side continues to expand as interoperability standards like Matter lower the barrier to building a multi-brand smart home, and as healthcare systems increasingly rely on remote monitoring to manage patients outside hospital walls.