The app is universal and runs on both iPad and iPhone. In fact, the camera in the iPhone is what ends up being the real "Camera for iPad." Installing the app on your iPhone and iPad allows the two devices to find each other via Bluetooth. When they're linked, everything that the iPhone camera is seeing is transmitted to a window on the iPad. Press a button on the iPad, the iPhone snaps the photo, and then the photo is transferred -- slowly -- to the iPad.
The idea is pretty cool, and it does provide a way to get photos into your iPad until that Apple Camera Connection Kit actually hits the stores. The slowness I'm talking about in the previous paragraph is not a fault of the app, but the fact that Bluetooth is being used for the file transfers. It doesn't have anywhere near the speed of Wi-Fi, but you will be able to shoot and transfer photos anywhere; there's no need for the two devices to be on the same Wi-Fi network.
Possible uses for this could include the ability to set up a local webcam, a clever way to catch an iPhone thief in the act, or it could be used just for fun; the kids would likely enjoy being sent out around the house to act as remote cameramen. When you see something you like, you take the photo. It's a lot of fun, and inexpensive as well (provided you've already spent the $1,000 or so dollars for your iPhone and iPad).