PacAce wrote in post #5695507
That's just a misconception that the RadioPoppers can do ETTL. They don't. All they do is "sense" the IR command signal generated by the master like the ST-E2 and transmit that signal via RF over to the receiver unit which then converts the signal back to IR for the slave flash to see. It's the master that's actually doing all the ETTL processing. You can think of the RadioPopper more as a repeater relay.

Replace "do" with "allow" then. The fact that RadioPoppers need to sit on a master device - ST-E2, 580EX, or a Nikon equivalent - says little about the functionality they provide. That functionality certainly comes at a price, but none of this gear is cheap -- even Pocket Wizards, which are only capable of "relaying" a simple pulse, are ridiculously expensive. Radio Poppers "relay" a much more complex signal for a similar price and only need a master device to deliver VERY reliable off-camera E-TTL!
I agree that confusion abounds about the need for a master device tho 
Wasn't trying to perpetuate said confusion here 