B&H has the Vello FreeWave Aviator Wireless E-TTL II Flash Transceiver/Receiver Kit for $109.95 (reg. $289.95). This system has 4 channels and offers 3 different groups for Canon E-TTL II Speedlites. It operates at 2.4Ghz and has a range of 300′. Check it out here at B&H Photo.