[17R3W]

I'd argue it is...
You could use it in the car with any video game system you want.
Not to mention the Game Cube has battery pack you can get, but I imagine it being great for filming on site.

It's nice to have a monitor (in adition to the LCD screen on the camera) and it lets people working beside you get an idea what your filming, but they can be big/costly.
This is cheap, replacable and has multiple purposes.

But your right, becasue you do need another device to use it, (as it doesn't have a built in tv tuner) it isn't that portable.