I have used the Aokatec GPS units for my D800/E cameras. I only use them maybe 10-14 days a year, so I can't speak about long term reliability. It recieves GPS and records direct to camera through 10-pin. They work.... so far.
I do not know what advantage bluetoothing data from a separate unit has over the all-in-one approach.
http://www.aokatec.com
I've had the AOKA for some time now.
Very heavily used.... and abused a little bit.
I have one of the early units, purchased for the D300 when it was fairly new-ish.
The square block design wouldn't fit nicely on the D800, as the D800's front body design was more sculptured compared to the D300(and previous Nikons with the 10 pin port.
AOKA fixed this with the newer models, but mine still worked, but had to be forced onto the body to do so.
The (old model)AOKA had to be filed down a little on one corner to fit properly, which I proceeded to do, but did so with a bit too much vigour!
On the very corner of the body I filed down but made a very small piercing into the body. Up till this point the insides seemed pretty well sealed.
That was in 2012.
While I don't get the time and chance to get out and about as I'd like too, I have done enough to warrant the comment that the little AOKA is pretty tough!
Well it beat my D800 for toughness too .. in a battle between 10 pin port toughness
(I had to deal with the dreaded D800 10 pin port 'collapsing in' syndrome)
Main reason to go with a Bt/wireless solution is for the sake of battery consumption.
I used to have a wired GPS setup with the D300 and I'd barely get a couple of hundred shots in a single battery charge with the GPS connected by wire. (note that most, if not all, GPS devices will need a power source, which usually comes from the host .. ie. camera)
With the bluetooth GPS setup, the bt receiver(ie. AOKA or foolography) only uses a very low power bt comm link. The drain on the camera battery by the bt device is so small as to be insignificant.
I've gone two days without battery drain on both the D300 and D800.
In terms of exposures, the difference is (as an example), on the D300 I used to get about 200 exposures with a wired GPS, but with the Bt setup, I'd easily see more than 600, and sometimes over 800 exposures with the AOKA and Bt GPS ... and only charged the batteries a couple of days later to be sure I had a full days charge the next day.
Some things to note about GPS compatibility too tho, and that is the communications between the GPS and the camera. GPS uses a system of communications called NMEA.
I can't remember the exact numbers and types, but Nikon cameras use an older version of NMEA, and only understand this version.
Some smartphones( I know Apple does this) uses a newer(or maybe even proprietary??) version of NMEA.
There was a discussion about this on the old NikonGear.
If you try to connect any GPS device that only outputs newer NMEA sentences, it seems as tho the data doesn't get through to the camera or that the connection hasn't been made. It most likely has been made, and is getting through .. it's just that the camera doesn't know what it is and hence can't use it.
Also; it's not always as simple as just using the output of your smartphones GPS, as not all can actually output their GPS data .. in other words, those smartphones can only use their GPS data internally.
For me, my primary concern is battery life, as I use the GPS feature mainly for landscaping. Sometimes it's not always convenient to have access to a charger of some form. The reliance on a smartphone for the GPS data will be subject to how long the battery can sustain using the GPS and running an app to output that data over the wireless link. If battery life(eg. more than 6 or so hrs) isn't an issue, then the smartphone solution could be convenient as you already have one device .. and so the foolography looks to be a nice solution.
Note on the foolography system(s).
They still have the older(original) D200+ device for sale, but appear to be getting a new Unleashed product out to market soon. I can't see much in the way of details on the new one, but for smartphone GPS usage, you would need this new Unleashed model.
The original D200+ model will only work with a dedicated GPS device. Also, if you ever need it to fit onto a D800, it seems that it also requires the "D800 modification" like the older AOKA does .. which is simply a sculptured profile on one corner of the device.
