Most ICS vendors are now offering wireless sensor offerings, and some are climbing on the IoT (Internet of Things) bandwagon. Why? I'd ask the snarky question, "Why not?" but the fact is that the technology is becoming inexpensive enough to be everywhere.
What does this mean? Well, my house has several Z-Wave (Zigbee) devices that are connected to my alarm system. I don't have alarm system wires running everywhere. Many people have these devices and don't know it.
In a plant environment, you can build more high fidelity models with more sensors feeding information to them. You can make changes in your process knowing that you actually have data, and not just guesses. You can make your plant run more productively and more profitably.
Here's the information from IBM and a wireless communication company called LIbellum: