Here's another guest blogger entry by Hans Odenthal who wrote abut Sioux.net on track some time ago:
Hans Odenthal has managed to connect the EV3 to a PC and is now able to send messages back and forth between a hand-written PC Application (C#) and the EV3 using Bluetooth.
Since there is no documentation available on the Internet about the protocol, Hans had to figure out the protocol by reverse engineering the Linux code that is running on the EV3 brick.
More details can be found on his blog about his train automation project.