This is kind of an old thread, but I just found this website. I'm a smartthings user and they have a arduino shield that's zigbee based called a thingshield. They sell it in their online store for $35. One user on their forums said that although it's a steep price to pay if you wanted to set up multiple controllers, you might be able to use a single arduino/thingshield as a gateway to the hub and have the rest speaking through that one via RF or I2C. I do not know how that would be set up, exactly...