More on BLue2CAN - Camera Area Network for Nikon
The Blue2CAN connects automatically (and silently) to ANY Bluetooth GPS in range (within 10 m of it's location) The idea is that in the rare event there is more than one Bluetooth GPS in range that any one will do as it's "close enough". However these receivers only connect to one device at a time, so the GPS device must be on, in range, and NOT connected to something else, it's most likely yours. If the GPS is separated from the camera Blue2CAN loses the connection and starts searching again. If the same one, or a different one comes it range it uses it. The advantage is that it is AUTOMATIC, and therefore easy to use.
Connection speed is not really a problem because the Blue2CAN stays connected to the GPS as long as the GPS receiver is on, even when the camera is turned off (yes, Blue2CAN gets power from the camera even when the camera is off). In this way the GPS data is available immediately when the camera is switched on. Note that it is best to turn the camera off when you’re not shooting because the GPS does hold the meter on (Nikon's design) and the meter takes quite a lot of power. Fortunately Bluetooth takes very little power so it does not put much of a drain on the camera battery in any case. The drain is so small that the D200 camera battery can keep the Bluetooth radio working for more than 25 days (and nights). GPS takes a LOT more power, so the batteries in the Bluetooth GPS device will probably not last more than about 14 hours.
If the Blue2CAN is not connected to a GPS when the camera is turned off it will search for 10 minutes longer, if no GPS if found it will turn itself off. It will start searching again when the camera is turned on, and takes about 5 seconds to connect in this case. It usually takes GPS receivers at least this long to get a fix from power up, so when the GPS data is available the Bluetooth is already connected. I'm sorry if this description was too complicated, but the complexity was necessary in the implementation to both manage power and make sure no GPS data was missed when a picture is taken...
The two real advantages of using a Bluetooth GPS instead of a camera powered GPS are that 1) the power systems are separate. And 2) the GPS antenna can be placed in a good position regardless of where the camera is.
Power: The GPS must be on all the time to “keep a lock” otherwise you have to wait for the fix before you take a picture (not a good use model). The GPS takes a lot of power, so it can put quite a drain on the camera battery, if the GPS battery goes dead you can still take a picture, it just won’t be geo-located.
Antenna: To maintain a fix the GPS antenna must have a clear view of the sky, if your shooting from inside a car or other vehicle it’s better to have the GPS on the dash than on the camera. Also if the camera is “stored” between shooting where it will not “see” the sky, a camera mounted GPS will loose lock and may take to long to re-acquire when you get the thing out to take a shot.
Red Hen does offer a camera mounted GPS unit for the D200, D2X as well, it's called the "DX-GPS" we’ve had it available for some time, these are the things we’ve learned from use and customer feedback.