Numerous possibilities with a tablet that is made and/or a dock with HDMI or video (component) input. This allows:

1. Phones to output to a tablets' bigger screen
2. Laptops to use a tablet as an extra monitor
3. Gaming consoles to have a portable display
4. Camcorders and Cameras to be used as active surveillance or recording tools
5. Possible DVR capabilities when hooked up to a TV.
6. Possible recording capabilities when hooked up to any video or audio output system, including speakers and gaming devices.
7. Recording equipment such as mixers to be used to record directly onto the device.
8. ANY device with A/V output to use a tablet as an extension.

We already know this is technically feasible because high end laptops, DVR boxes, Slingbox, etc already has this kind of input. 

Some scenarios:

- edit a word document with your laptop while having a PDF open on your tablet screen
- musician could have sequencer open on laptop and synths and analyzers open on tablet
- graphic designer would have numerous uses for 2 screens
- a programmer could have code open in one screen and program running in another screen
- the same for 3D-designer