Steve,
NFC is good for only a few inches, but that's doesn't matter.
NFC, if you have the capability on your mobile device and an app that understands it, only sets up the real communication path. Basically it allows your mobile device and your camera to do this: "Do you have a WiFi connection?" "Yes I do, and here's how you connect." "Oh, okay. Let's now talk WiFi." That is it. There's nothing else that NFC communicates between your D7200 and your NFC-capable device. All the rest of the communication, either between your camera and Nikon's app...which ain't all that good...or a third party app is done with normal WiFi. BTW, there is an open source program called Airnef that's been getting some buzz. There are some threads on DPReview about it.
Now if you don't have a NFC-capable device you can still use WiFi and the above mentioned applications. The difference is that you have to set up the WiFi connection yourself, which means some more steps. At the end, there is no difference. You'll still be talking WiFi.
I haven't bothered to extensively test WiFi range, but it certainly works for several feet.
Someone mentioned that the Nikon app would only retransmit Live View...what'd you'd see on your LCD when you engage Live View...and take a photograph, but I had to go check for sure. It does allow a little more camera control, and it will allow you to take a photograph and transmit it directly to your mobile device.
I'll be honest. I don't use that functionality at all. I can sort of see the use if you wanted to take a photograph and immediately post it on Facebook or some other social media site. Personally I only shoot RAW and wouldn't post a photograph until I've done a lot more editing on a decent sized, color-profiled monitor. Frankly, from what I've read, even the "let's get it on Facebook" workflow is really clunky, far less convenient that just using a good smartphone.
The other use that I can see for transmitting your shots immediately to a tablet is to satisfy that art director or client who wants to see your work as soon as you press your shutter. You can keep the original file on your camera for post-processing, but let him/her have a handy way of seeing what you're getting in real time. I don't think this applies in your case.
If I understood your post correctly, you want to have, in effect, a remote viewfinder and shutter release. The Nikon app will do that and a bit more. Other apps add more features. For the Nikon app you have to use either iOS or an Android device. Other apps might run on Windows as well.
BTW, one reason I don't use an app is because I don't have enough arms. Unless I use a tripod to hold the camera, I don't seem to be able to hold the camera, the phone, and have a hand left over to press the shutter release.
Tom
