Here come 'Awareness of Things' gadgets

While nobody was paying attention, a wonderful new class of mobile gadget emerged.
These devices aren't wearables because you don't wear them. They're not "Internet of Things" devices because they don't have IP addresses. And they don't enhance the normal functionality of a smartphone like, say, Bluetooth earbuds or a tiny projector. Even more intriguing is that the actual functionality of these gadgets is very specific, but can be applied creatively to a huge number of jobs.
So what are they?