You have to ask about the difference between want to and need to. We have a portable support rig (about the size of a small semi-trailer) that is PLC controlled. Inside the unit there is a touchscreen workstation running the HMI that controls the machine, which operates as it is being towed down the road. There is an alarm beacon on the top, so if it went into alarm, the guys in the van following would see the beacon, call for a stop and investigate. Then someone came up with the bright idea "Why don't we install a wireless communication? That way we can see what it is doing continuously." So they bought a Wireless Access Point from Best Buy for about $50, and added a laptop running the same HMI. Now that wireless communication capability was advertised to the customer, and it turned from want to into have to. That is when we learned about all the pitfalls of wireless and an industrial control system. We had to design a system that would be robust and immune to noise and the potential for a random hack attack. We are using a pair of Cisco Aironet wireless bridges, set up with direction patch antennas, multiple authentications and a 100 MB Ethernet network. Not cheap, or but it works flawlessly. So you have to ask yourself, do I want to or do I have to, and how critical is the system?