I just spent a weekend discussing this at Philly BrickFest (after having a few conversations with Peter from S-Brick) which is making me feel like a behind the times schmuck because I am just now getting the devices to work on my layout with the latest iOS9 release along with the latest version of the S-Brick app. My personal goal with the S-Brick is that I will be able to control multiple motors in multiple locomotives in a single consist without worrying if the IR Receivers are getting the same signal and set to the same power levels. Using synchronized, powered units at both ends of my tender on the SpaceTrain is the only way that I can keep the inertia of the heavier car from totaling the MOC everytime I attempt to slow down the locomotive. Inertia is simply a mean and cruel witch.
Back to the Bluetooth concept on a large LUG layout is that typically, the Bluetooth signal from many of the cellphones and tablets on the market are not strong enough to maintain a connection with the S-Brick devices as they travel around the layout. Also, some devices (like my iPadAir2) have a very strong Bluetooth signal which could interfere with the connection with my iPhone 6S Plus connected to my locomotive on the layout. It would be pretty nasty to have someone walk by one end of the layout with a Bluetooth connected Apple Watch and have that device interfere with the connection between the SmartPhone/Tablet controlling the trains as they pass along that end of the layout. WiFi may be the better option if I cannot work out the issues with interference on the devices. I will let everyone know my progress with my experiments on the S-Brick and hopefully I will have some solutions running by the end of the year. If I get lucky, I might be able to run some full scale experiments when we have out layout at a train show late this year or very early next year.