Hi Rex,
Thanks for such an awesome effort on this plug-in.
I've gone ahead and given this a shot, I'm very new to Vera so forgive my ignorance. I've ordered all the parts, put them together, and followed your instructions. I have got the sketch to upload successfully to the Arduino, and I can communicate successfully over WiFi with the USR unit.
Unfortunately, after adding the parent and child devices per your instructions, I am not able to control them

Whenever I click a child's button, say 'up', the parent device says 'WiFiRTS Failed!' I also note that there is no lights flashing on the USR to indicate data transfer (unlike when I browse the USR's webpage).
I've double checked I've entered the right IP and port, and restarted luup a dozen times, but I can't get the message to go away. Note that I have a Vera 3 and I've set it's IP address as the 'Server Address' in the USR webpage, but I've set my WiFi router's IP address as the 'Default Gateway' in the WAN connection type.
Do you know what I might be doing wrong?
Thanks again, Stibbzy.