There are a few app such as CamCharger or Nikon WMAU that makse an interesting but cumbersome attempt at a wireless app for tether shooting. But for me I find that wireless is far too unreliable and slow. The time where it would be most useful, i.e., when shooting freehand outdoors, it is pretty much useless. In a studio, having a cord attached to the camera is not a big problem, however. This would allow much faster download of images.
There is one really simple solution that almost gets the job done: Use the iPad photo adapter which allows you to connect the camera to the iPad using the standard USB cable. When the iPad sense that a camera is connected, it automatically opens the iPad Photo app which then shows you thumbnails of everything that gets recorded on your camera SD card. Great, cheap and easy.
The problem is that if you want to actually view that image at normal size you have to select it and click on Import, then go into the Last Import album and view it there.
Does anyone know of a simple little app that automatically downloads and displays the jpeg from the card on the iPad? The basic Photo app is almost there but not quite.