The only problem I have with the GPS unit is its location, you cannot use an external flash.
Are you saying you can not use a flash because it is attached to the accessory shoe (I assume that is the hot shoe)? Because you can also teather it with a USB so your flash can be connected to the hot shoe.
5DS R, 1D X, 7D, Sigma 10-20mm f/4-5.6, 24mm f/1.4L II, 16-35mm f/4L IS, 24-105mm f/4L, 50mm f/1.8, 100mm Macro f/2.8L, 70-200mm f/2.8L IS II, 100-400mm f/4.5-5.6L, 580EX-II flickr