Current best way to accomplish this. I use my favorite D-3 which has no WiFi options Thanks for your time.
The Nikon D3 uses Compact Flash for storage of image data, I believe. It MIGHT be possible to use an SD to CF card adapter which would them allow you to use an SD card with an integrated WiFi hardware to connect via WiFi with your mobile phone. It also MIGHT be rather slow to transfer image files, depending on their sizes. We talking large RAW files, or small or medium jpgs perhaps?
I have never done this, but I do know some folks have had pretty good luck with SD type cards with their built in WiFI networking hardware. It might be worth a try.
Perhaps there are readers here with actual experience with SD cards with WIFI adapters in the D3.
I don't think there are reliable CF cards with WiFi adapters, at least none that popped up in a google search for me.
An alternative that apparently works pretty well, is a CF card reader that plugs into an iPhone - check Amazon for CF card reader for iPhone ( also reads CF, SD or micro SD cards) and is cheap at 25 bucks. You have to take the card out of your camera to transfer, but it does seem to work pretty good according to reviewers on Amazon, especially to an iPad Pro or an iPhone.
I use the Eye-fi SD card in my Canon 5D MKIII. It will wirelessly transfer images from my camera to my iPad or my phone as I take them. It works pretty well, for the most part, but isn't perfect. I don't know if they make a CF card with this feature though.
It is finally time to revisit this. While it was already possible to use a card reader (and Apple adapter) to copy photos from a camera card to an iPhone, with this month's release of iOS 13 you are no longer forced to copy them into the Apple Photos app. You can now copy them from the card to any folder you have in the Files app. From there you can preview them, move them to a computer, or open them in any iPhone photo editor.
It's working on my iPhone SE, using the Apple Lightning USB Adapter (the one with the Lightning port to provide power), to read cards from my pre-wifi old Canon DSLR using a cheap USB card reader. It's even nicer on the iPad because the screen is big enough that you can drag and drop between folders in the Files app.