WiFi SD Cards - What do you know?

While roaming around and shooting in FL last week, while I was firing away with my camera my wife was often next to me trying to grab stuff with her Android phone and getting frustrated. It was then that I finally realized that I might have a use for a Wifi card, if only to fire off jpgs to my iPhone and/or her Galaxy. My thought was to put one in the second slot on my D600 and when I needed it just set the mode to RAW+JPEG with the JPEG's going to the second slot and then off to the phone(s). Seems pretty straight forward and something that could easily be turned on/off, and those photos could then immediately be shared with family/friends rather than waiting for me to get home and sort through the RAW files and export pics to send out.

My primary question regards battery drain with the wifi card. I would assume it requires a little more juice than the standard SD card and will drain the battery quicker, but the question is how much more quickly? Can the functionality be "turned off" when not in use (I'm thinking no)? I could always pull the card when I don't need it and only stick it in when I believe I might, but that runs the risk of losing it.

Anyway, I'd appreciate any insight ore positive/negative experiences any of you might have to share regarding using them.

Also, Eye-Fi seemed to be the only one out there for a while, but now I'm seeing Transcend cards, so if you have any experience with the latter I'd appreciate hearing about it.

(answering some of his own questions...part 1)

Found this in an Amazon review of the Transcend card, submitted by the manufacturer as a comment to a complaint that it doesn't work with a D800:

For Nikon cameras, you have to enable "Live View" shooting mode or adjust the power settings so that the cameras will not go into power saving and can provide sufficient power supply for the Wi-Fi SD card to connect wirelessly.

Further down it links it to the sensor off time, which must apparently be set to infinite. I suspect that between the options of Live View (not!) and no sleep time for the sensor that this may not be a utopian solution for me. Gonna keep digging...

With the Eye-fi card instead of transferring all photos you can set only the ones you want to transfer via the photo lock. I was taking a lot of photos last year at CES and transferring them on the fly. The biggest problem I had was actually the phone. When connected to the camera via wi-fi it couldn't use 4g. So switching between the two was a real pain. See blog here on how I had it setup: http://nikonites.com/blogs/jdeg/77-my-mobile-4g-dslr-rig.html

Thanks. Hadn't thought about the ability to actually use the phone as a phone while connected to the card. I wonder if it's an issue with iOS? I suppose no solution is perfect.

No...It's not an IOS problem as much as a basic design issue. The same thing happens with the GoPro cameras... The phone has to connect to the wifi pack, which means it has too give up the 3G/4G/Wifi connection... I imagine the phone sees the card as a Wifi connection, and can only make one connection at a time...

Interesting that, as when I'm using my phone with WiFi, I can still use the 'phone' bit (makes calls, receive SMS etc).
Yes, you can't use the WiFi with the camera and use the phone at the same to surf the net, or other data communication reliant services.