The title pretty much says it all. I have this working and I will do my best to explain the entire process. But first, the disclaimer.
The following is not an endorsement for any product real or imaginary. No user-serviceable parts inside. Any resemblance to persons living or dead is purely coincidental. Continued reading constitutes acceptance of agreement. This website, author, ISP, family, friends, known acquaintances, the dog that peed on your shoe, all known humans, living or dead (excludes zombies) are held harmless. This disclaimer does not cover misuse, accident, lightning, flood, tornado, tsunami, volcanic eruption, earthquake, hurricanes, or other acts of God, neglect, damage from improper use, incineration, or robo-calls. The fact that the content described here works is a miracle on an order of magnitude that is seldom seen in a single life time. The fact that the content described here worked for me is in no way a guarantee it will work for you. That fact that the content described here did not nuke anything, cause smoke, excessive cursing, or human or animal sacrifice is not a guarantee in whole or in part that any or all of those events may not befall others who attempt to reproduce the results. Buyer beware. No guarantees, real or implied. Use at your own risk.
Yeah, that was messy. While it is partly humor, it is also important enough that I will repeat – USE AT YOUR OWN RISK.

In addition to a Nikon D700, an Eye-Fi Connect X2 Card, and Extreme SD to CF Type II Adapter you will also need a utility knife, sharp scissors, and a thin piece of plastic (I used the packaging from the adapter). I also suggest you find an old Compact Flash Type 1 card you won’t mind sacrificing.
All you need to know is contained in two videos. The first shows how to disassemble the adapter. The second is optional but a good safety measure explained below.
Note: the adapter I purchased did not have the thin plastic insulating film shown in the first video. It was not critical but something you may encounter.
The D700 memory card ejection button is connected to a small frame deep down in the CF slot. The modified adapter will likely catch on it. To solve this, you need to cut a thin piece of plastic to act as a guide. I used the packaging from the adapter. Cut the plastic almost as wide as a standard CF card. Cut it slightly longer than a standard CF card. Now drop the thin plastic rectangle into the CF slot on the D700 such that the end sits between the pins and ejection frame. This will allow the modified adapter to slide into the camera without getting caught up on the ejection frame.
The second video above describes how to cannibalize an old compact flash type 1 card.
I highly recommend this procedure. It was not absolutely necessary – I tested the adapter + eye-fi card after completing the instructions in the first video and it worked. However, here is your important safety tip – IT IS VERY EASY TO BEND PINS INSIDE THE CAMERA WHEN INSERTING THE NAKED ADAPTER. You would be seriously bummed if you did that. You might get lucking and insert it once or even twice but very soon, you will be sending your D700 in for service because you mushed a pin.
The use of the CF-1 frame aligns the modified adapter in the slot. There is a much smaller chance of messing up your camera if you complete the steps of both video one and two.
In the midst of all the dissection, it is easy to get confused which way is up regarding the modified adapter and the cannibalized CF-1 frame. Below is a picture of the finished setup inserted in the D700. Use a good memory card as a reminder of which way they go in and then assemble all of the parts to match the end result.

Addendum: The D700 really likes to power down the CF card (and thus kill the juice that runs the WiFi in the Eye-Fi card. The easiest solution is to set the Playback timer to 5 minutes (MENU -> CUSTOM SETTING MENU -> TIMERS/AE&AF LOCK -> Playback). This will not affect battery life when shooting since the “review” timer is a different setting. The playback timer affects when you hit the “play” button to review past shots. Setting it to 5 minutes lets you power to Eye-Fi card and then go to your iPhone or iPad and start the Eye-Fi app to transfer images. IT will often take 30+ seconds before the first image transfer so give it time.
One last time – Don’t blame me if you screw up your camera, Eye-Fi card, fingers, or anything else involved in this post.