The WU-1a WiFi adapter is at least a step forward from the $400 vertical grip on my D200, but I believe it's still a bit lacking. If Nikon is interested in the product architect for their wireless connectivity lineup, I'm more than happy to oblige...
The WU-1a is pretty darn tiny. It's unobtrusive and plugs into the proprietary USB port on the Df (again, Nikon I can forgive a lack of a micro USB connector given the long product cycles but forgoing a standard mini USB?). It comes with a small case that will help protect the connector when not in use, you can either use a small tether (which does make your camera strap look like a bit like a charm bracelet) or mount the case onto the camera strap directly. Installed, dangling, or on the strap there isn't much added bulk or annoyance.
Here's where we start to see issues. The WU-1a is a tiny little access point, it's not a WiFi adapter. This means that you've got a choice, you can connect your phone/tablet/laptop to your camera or you can connect it to the Internet. It's possible that the software will allow a device with LTE connectivity to connect to both the camera and LTE at the same time (I can't test since all of my access is via MiFi), but I doubt it. If Nikon would allow it to be a WiFi client I'd be all set.
The software on my Nexus 4 is pretty poor. The WirelessMobileUtility is truncated to a simple "wmu" where the lowercase letters appear more lazy than stylish. Connectivity is not reliable, LiveView doesn't seem to work, and downloading images takes forever. All-in-all, it's a decent, albeit roundabout, way to have a remote shutter release but that's most of the use case I've found for it.
Having tried this with my Nexus 10, I may need to experiment a bit more. On the N10 the software seems much more reliable and LiveView works, but you've still got the issue of needing to choose between Internet access or camera access. I'm considering using a cheap and semi-compact N7 which will connect to my home network or the WU-1a, this will give me the ability to use the WMU when away from home but when I get home and turn off my Df things should automatically upload to Google+.
There is an alternative in the form of Helicon Remote. It's a bit pricey for the full version, but much more feature rich and professional than WMU and really the free version is not overly crippled except for RAW support. Unfortunately the WU series isn't natively supported, but it can be made to work. First, install the software and open it up. Next, connect to your WU-1a network. Now click the Tools tab and tap "Network cameras". Add a camera at 192.168.1.1 and call it whatever you want. You can select Nikon WT as the type and the port can't seem to be selected, but feel free to experiment with 15740 in your free time. I had issues here where the camera didn't seem to add. I ended up rebooting my tablet and it showed up, but your mileage may vary.
Now when you open the app you can click the "Select a camera" button under the opening "Exposure" menu and select the camera you just entered.
How to Fix it
This sort of thing can be fixed pretty easily. But only by redesigning the product, not by the end user.
- First, you need to enable client mode so the camera can connect to a pre-existing WiFi network. This solves all of my problems since I'll have my MiFi device, but it will also solve problems for studio shooters who want to send pictures to their laptops for instant review and edits.
- The wireless device or the camera needs to be responsible for downsizing the images sent and there needs to be better control over this. I would like to see JPGs at 3-5MP sent to my phone in realtime, but full sized JPG and NEF files sent to my PC. Bonus points if full-sized JPGs are sent to my phone in the background.
- You need something more than WiFi to control it. Bluetooth is enough for camera controls and should be reasonable for downloading images if they're kept small. Live view may be an issue over Bluetooth but even if the frame rate is horrid I think it should be doable.
- Pop in an NFC tag and appropriate software and you could easily tap your phone to the side of the camera and switch to a WiFi connect mode.
- And, of course, just build it into the camera itself. When you're charging $3k for a camera having a disabled WiFi chip in it (and GPS for that matter) is dirt cheap even if only a few use it. These things are slapped into $200 tablets with no issue.
I've ordered an Eye-Fi card to try it out. The Pro model supports connecting to existing WiFi networks and hopefully the overall usability has improved since the last time I tried it with my D200 using a CF adapter (didn't work at all), and my wife's D80 (worked, but unreliably since the SD card lost power before the transfer was complete). The Df has some Eye-Fi specific menu options and is explicitly mentioned in the manual so I would hope that the Df and Eye-Fi play well together.
The Eye-Fi solves part of the problem. It does connect to a pre-existing WiFi network (however, you need a Windows VM to get it working). It stores files in /sdcard/Eye-Fi which means that by default they won't get backed up using Google+, but there is a setting under autobackup to enable this as well as the /sdcard/Pictures directory where screenshots live. So far, so good. Backup, however, is pretty slow still. I'm worried that it's going to the Eye-Fi server as a sort of intermediary, I do see a lot of traffic from my Eye-Fi to my phone when it's backing up rather than via my router and it only seems to back up when my phone is on the same WiFi network as the camera - both of which are very good signs for me.
The Eye-Fi uploads aren't 100% reliable. I suspect what's happening is when I take a slew of pictures and then pause for an extended period the Df is shutting off power to the SD card. This isn't nearly as bad as the D80 which did it within seconds, but it is something to worry about if you're sending NEF+Large/Fine JPEG and tend to shoot in bursts. I haven't been able to replicate it if I touch the shutter button every few minutes to wake up the metering and I've recently turned off JPEG shooting which saves me about 25% of the transfer time.
Still, it's reliable and geotagging which is good when I'm at home.