Small Radio controllers, that transfer simple serial signal. 128 different channels. Mainly used for short ranged one to one communication. Cost about $20 on amazon and pololu. Small and easily interfacable with Arduino like microcontrolleds. Range is 15 yards.
Similar to a Xbee, connect the RX & TX pins on the wixel to the TX & RX pins on your microcontroller.
Formating and basic set up (tba)