Are single boards always necessary when implementing an IoT connection? Can they be substituted by normal smartphones in, let's say, a business setting so as to communicate to POS/Internet-enabled sale system?
I'm not well oriented with Android Things. I just saw the option to include its support when creating a new application in Android Studio. Any and all helpful advice is welcome.
The device itself isn't really particularly important here. While the boundaries between 'IoT' and just a normal network connection are a bit fuzzy around the edges, the general consensus is that the main requirement is that you're interacting with the physical environment in some way.
How you reach that goal is up to you, and so it doesn't really matter if you use a smartphone, a single-board computer or even a server rack. But what distinguishes IoT from traditional computer networking is the fact that you're connecting physical devices to a network for sensing and control.
Single-board computers often tend to be more useful in that case; for example, the Raspberry Pi has many GPIO pins which can easily be connected to a circuit to control another device. Your phone almost certainly does not have GPIO pins that you can use to connect to other devices. You would need to find some other way of connecting the phone to the environment to be able to control other devices, so it adds an extra layer of complexity. That's why single-board computers are far more popular in this space.
Additionally, a smartphone likely has features that wouldn't be needed (e.g. a touchscreen), adding to cost and complexity unnecessarily.
Honestly, a POS system would be better thought of as a traditional computer network than trying to call it 'IoT'. Tracking packages with RFID chips to connect 'things' to the Internet on the other hand would sound more like an IoT use case. Notice the difference here — just connecting traditional devices to a network would generally not be considered IoT, because it doesn't connect physical devices that would otherwise remain isolated from networks.
Short answer is NO, IoT is really a concept about "things" communicating (usually over the internet) with other "things", by this definition a phone can just as easily be a thing as a raspberry PI, or a PC.
IoT as a concept is device agnostic.
From an Android Studio point of view, adding IoT support means that common protocols and support libraries such as MQTT will be added to the project so that you can make use of them in your application.
If you have a need to implement an IoT Connection and the rest of your code or logic can be executed from the phone or whatever the device is, then go for it, congratulations, your "Phone" is now a "Thing" that can be connected.
Is it still IoT? That becomes a subjective discussion, but usually an irrelevant one. From a purists point of view IoT implies Device-Device connections, where each device knows how to perform specific operations and either does this on a scheduled or triggered basis, or after receiving a command from another device. So an IoT solution will usually involve a lot of satellite devices performing discrete operations or relaying telemetry and there will be separate processes or entities that coordinate between these "things"
In a practical sense, you will find that many IoT implementations will involve micro-controller devices like Arduino or mini-pc / compute boards like Raspberry Pi as they provide a hardware platform that simplifies how we can get our logical code base (software platform) into a specific environment that can interface with hardware to collect telemetry about the physical world or that can otherwise interact with it. But that is only a subset of possible applications of IoT.
Are single boards always necessary when implementing an IoT connection?
No, Single Board Computers aren't necessary. Single Board Computers provide a very effective way to build a proof of concept, and are instrumental when the developers are trying to create the software stack. But, for a mass scale production a specific design is created. A specific design has benefits of power, thermal and performance. For example:
Can they be substituted by normal smartphones in, let's say, a business setting so as to communicate to POS/Internet-enabled sale system?
Using a smartphone will be a overkill, as smartphones are built to be multipurpose. And re-purposing a smartphone would hurt the solution in following aspects:
