The SMART Document Camera is similar to an ELMO in that it will display anything you place in the viewing area; the difference is that the SMART Document Camera displays images onto a SMART Board interactive whiteboard where you can capture images within the Notebook collaborative learning software.
The ability to manipulate the image within the Notebook program gives this device many more functions within the classroom as compared to an ELMO. You can also record using the SMART Board Recorder software so that students who are absent can also view the lesson.
For more information:
http://www2.smarttech.com/st/en-US/Products/SMART+Document+Camera/default.htm
To see the camera in action: