I have both. Used the Eye-Fi in my D7000 for a couple years. The one thing it didn't do was turn the tablet into a shooting aid. Focusing and framing done through traditional methods (through viewfinder or live view.)
The Eye-Fi X2 Pro 8GB card DID turn my tablet into a 10.1" instant chimp monitor, though. If you set the eye-fi into slot 2, shoot jpg small on it can get transfers to the tablet in under 3 seconds or less... Almost instant feedback on your shot.
Now I have the WU-1A to go with my new D7100. This doesn't really work the same way as the Eye-Fi card did. I can use it to either TAKE the photos or PREVIEW them. But, there do seem to be some serious drawbacks to the functionality... I also use the tablet and remote tethering software to do a few things, like Focus Stacking, etc. with my tablet. This is what I envisioned the WU-1A to be like, and it is sort of like tethered without a wire.
1) When you set up the tablet to use the WU-1A for the shooting session you HAVE to make sure you are in the correct shooting mode, with all the settings you will use for the session. Once you have the camera and tablet linked you are stuck. Can't change modes, iso, etc. Have to get out of the photo taking mode of the software on the tablet, make the changes you need for the exposure, go back into software, etc.
2) Zooming in on the liveview display on the tablet doesn't get that high of a level of zoom. If you are doing a stack or critical focusing, can't really zoom in to check where or how well the focus is. You CAN zoom in, but not like some of the other software options for tablets.
3) Peviewing shoots taken has the option to preview all the photos on the camera. It tells you which are raw and which are jpg. BUT unless I'm mistaken, it only sends the jpg embedded in the raw file to the tablet during a preview.
4) Can't tell software to use the contents of one card or the other. I shoot Raw to card slot 1 and jpg small to slot 2. When it shows a directory of the photos on the camera, the software shows all the photos taken, by name order (or time shot, same thing, basically) mixing up the raws with the jpgs.
It's a kind of cool little toy, with some functionality. Since you are networked to the camera with this device on it, the software for getting other and more improved functionality is just a waiting game. There is at least one other piece of software that can use the WU-1A/B to control the camera, and with it you can set ISO, fstop, shutter, etc from the software. And the liveview zoom works as intended, too, so can check for critical focus, etc.
Overall I will probably still wire tether to my tablet until Helicon Remote for Android gets support for this device. shooting stacks with this software is just too easy!