What actually makes a device part of the "Internet of Things", as opposed to just being a computer on a network?
It senses or acts on the physical world, it is connected so that data leaves it, and it is one of billions of small, cheap, low-power units rather than one of millions of managed general-purpose machines.
The phrase is easy to use and hard to pin down, so it helps to hold three properties together:
- A foot in the physical world. An IoT endpoint has sensors (temperature, humidity, pressure, light, motion, acceleration), actuators, or both. Its purpose is to turn physical state into data, or data into physical change. A laptop is on the internet; a soil-moisture probe is of things.
- Connectivity as the point, not a feature. The data is only valuable once it has left the device and been combined with other data — so the device exists inside a pipeline that runs to a gateway and on to a cloud backend.
- Constrained, numerous, unattended. Small form factor, low cost, low power, often battery- or harvesting-powered, frequently with no screen and no keyboard, deployed in places nobody visits.
Across the classic application domains the same three properties recur with different payloads:
| Domain | What is sensed or controlled | What the value is |
|---|---|---|
| Smart homes | Lights, locks, heating, appliances | Comfort, "intelligence and lifestyle" |
| Transportation | Vehicle state, position, traffic | Internet-enabled communication between vehicles and infrastructure |
| Retail | Stock, footfall, checkout | Intelligent cloud services on top of shop data |
| Industrial | Machine state, production line | Machine-to-machine (M2M) communication, productivity and efficiency |
| Smart energy | Consumption, generation, grid load | Power awareness and energy saving |
Cutting across all of them are four concerns that every IoT design has to answer: user experience, connectivity and manageability, data analytics, and security and trust.
Tip: if you can remove the physical sensing or the constrained hardware and the system still makes sense, you are probably looking at ordinary distributed computing wearing an IoT label.
Go deeper:
Wikipedia — Internet of things — the definition in full, plus the application domains and the privacy and security debates that follow from them.