This photo is one I took as a test of a wireless "tethered" shooting set-up I have going here. The ingredients are: my DSLR (in this case a Sony A550) with an Eye-Fi wireless SD card inside; and an iPad running the PhotoSnitch app.
Once it's launched on the iPad, PhotoSnitch communicates with the Eye-Fi card and vice versa, so that I take a photo, and a few seconds later, the photo appears on the iPad's screen (inside PhotoSnitch) where I can review it on the iPad's nice and relatively large screen rather than using the high-res but tiny screen on the camera.
I had a wee bit of trouble setting PhotoSnitch up initially. If you have previously configured your Eye-Fi card to send photos to your computer, you have to mount the card on the computer first, open the Eye-Fi Center software and basically follow the instructions to break that link. Only then do you put the card into the camera, launch PhotoSnitch on the iPad, and finish up the connection from there. It was this part that I had a little trouble with, but somehow—to be honest, I'm not sure how—it worked itself out and now it works terrifically.
For studio portraits, this can be really nice. It lets the client-subject see the photo right away. Whether it's so useful for the photographer, I'm not sure. I do not generally "chimp" my photos, at least not excessively. I can usually wait to get the photos on to the computer for review.
NOTE that ShutterSnitch and Eye-Fi require a Wi-Fi network. The camera isn't talking directly to the iPad; they are both talking over the network. Too bad the Eye-Fi card doesn't support Bluetooth. Anyway, I understand that you can buy a small portable router that would let you create a not very "Wi" Wi-fi network anywhere. Sweet.
A final point. This isn't "tethered" shooting, at least not in the traditional sense. It's called "tethered" shooting because in the past, you connected the camera to the computer via a cable (the "tether"). I suspect cable would be faster, but it comes with the risk that you'll trip over the cord and pull your computer on to the floor.