Here's a neat iPad and iPhone app I heard about from Stu Maschwitz over at ProLost. It's incredibly useful for adding all kinds of important slate information and the iPad makes a perfect slate. Some more information: 

"Along with a color chart and selectable running timecode, DSLR Slate has all the traditional items for input such as Scene, Take, Framerate, Director, etc. DLSR Slate also provides unique items aimed specifically for DSLR cameras such as ISO Speed, Aperture, Shutter Speed, White Balance, Lens, Filter, and more. While being invaluable on set, these items also prove useful when shooting tests in varying lighting conditions. 

Since there are so many items to show the camera, we’ve come up with a new way of displaying the info. While in SLATE mode, you will see only the traditional items displayed. These items are Scene, Take, Memory Card (Roll), Director, Producer, Project, and Date. Those are the pieces of information that editors use most. Once the camera is rolling, click the START button and a quick burst will begin, flashing all items within about 2 seconds. This allows the camera to “see” each item for at least a few frames, ensuring that all of your information will be captured by the camera. The quick burst is then followed by a Visual/Audio sync and the traditional items will fade back in, ending the slating process."

For more details, head over here.