Does anyone use Eye-Fi cards or other wireless transmitters? Are they just for wireless transmitting of image files or can they be used to control the camera similar to the built in wi-fi on the Canon 6D?

I see that the Canon 5DIII is "optimized" for the Eye-Fi card, but it seems that is still just for transmitting of image files and not control. If anyone uses Eye-Fi cards, how do you like them?

Just wondering. Thanks,
Brant