3dscapture.com

Do you think it would be possible to even do a capture card for the Wii U Gamepad?

Yeah, it's possible. I picked up a WiiU a while ago to get a look inside. There's a lot more space inside compared to 3DS, which is nice. It should be easier to do a pass-thru design similar to the DS board making installation easier.

Great thing, buying a new GamePad is currently not even possible.

You are most certainly a very innovative genius, if you created a capture device for the Wii U gamepad that would just be incredible, for many people would just attach a Go Pro to it and record.

How much would you charge for to install one if you ever made them?

Can you not just get an elgato capture card or something like that ?

What's displayed on the television yet is not always the same as what is displayed on the Wii U gamepad.

Exactly, and the gamepad doesn't have AV out ports. You must have been thinking about the main console.

Depending on game, you can play games with 2 different Screens, games with a cloned Screen, games with TV off, or even games with GamePad screen off.
There are currently no games that fall under the last category, but Nintendo still allows that.

A good example would be Wind Waker HD. The gamepad will become the menu, and in a Let's Play/Walkthrough/Playthrough that only shows the main footage, nobody will know what's happening on the gamepad. It's like if you were to play a DS/3DS game and only show the top screen.