Can any handheld be used to watch video?

[Dantanna]

My son has a Leapster handheld game thingy and I was wondering if it would
be easy to modify it to accept a video input. With Gameboys, PDA, etc. is
it as simple as splicing in at the LCD with a video signal?

 

[gp]

There are handhelp video players available in the market ($200-$300). I
don't think they support video input