Nikon's genuine WU-1a wifi adapter for Df stick out from the camera body in a very odd and flimsy way. So, I don't think it is very comfortable to use.
The unit Bjørn uses looks much smaller and more unobtrusive. An Eyefi SD card may be worth looking at, too:
http://www.eyefi.com/
Recently got a WU1a with the 2nd hand D7100 I picked up, which also works with the DF
Agree with the observation on the odd way t sticks out, doesn't make the camera very comfortable to hold
Have been using Eye F Mobi cards with all my Nikons with SD slots (D800, DF, D7100), there is a SD to CF adapter but that lony works with a CF II card slot (which as I understand it is somewhat wider then a CF I slot) Got one, but haven't been able to get it to work with my D3 (that would have needed an update of my OS to El Capitan, and I'm not willing to risk that)
The cards work well, but you''ll have to live with its limitations e.g.
- basically only usable with 'JPG small' files (there is the Eye Fi Modi Pro which 'can' handle RAW files, but in my experience that takes ages per individual fies. Only shooting wire tethered is really fast enough for handling/transferring RAW files)
- having to regularly 'tickle' the Wifi connection to wake up and stay connected/get reconnected
- no 'instantaneous' transfer (takes about 5 seconds between taking the shot and full transfer of the jpg. That said, if you shoot a series and the Wifi connection is made, the files are transferred in a sequence quite fluently, without delay, one after the other)
- pretty flimsy built quality
The latter IMO is quite understandable.
It's basically only two very thin plastic halves which have to hold the Wifi bit as well as the memory, yet only be as thick as a regular SD card.
So after prolonged use/taking the card out of the camera all the time, you may risk tearing the two halves apart and consequently breaking the card (happened to me with my first card).
Solution is pretty simple though (if maybe not factory recommended)
Before the first time you use the card just stick a small, thin strip/piece of sellotape on it to 'tape' the two halves together. The tape can stay there and will prevent the card halves from falling apart in the long run.
But it's very convenient when eg working with a model, stylist, art director, to be able to show and discuss pretty fast after taking the shot what it looks like on a large screen (like a smartphone or tablet) without having to have an (expensive/big/heavy) laptop around.
I also use it when shooting events like eg catwalk, being able to show the results immediately after the show is a great way to make an impression
With a DF (which only has one card slot) it will have to take both jpg and RAW files, no problems with the writing speed though (on the D800's and D7100 I use one 'normal' card for RAW, and the Eye Fi just for basic jpg's).
Downloading the files (just jpg's, or jpg and RAW) from the card to the computer with a 'normal' card reader doesn't work in my experience (but I just use a humble HAMA 2.0 35-in-1) .
Fortunately I have a Macbook which has a SD slot, but there also are special Eye Fi SD to USB adapters for sale (prices are pretty cheap)