SCREEN SPECIAL EFFECT HELP

i want to make a special effect… when we loosing signal there is a kind of griching on the screen…i want to put it on my screen but i want to be able to see a little bit my player and play like…to sum up it a kind of special video efffect on the screen but we still can see what going on in the game…
alpah video i dont know how to say it

but i dont know how to do it ,make or find and pu it in the game
HELP PLZ

If you are using Unity pro then have a look at some of the image effects: http://docs.unity3d.com/Documentation/Components/comp-ImageEffects.html
One of them will probably do what you want.

If you are using the free version then I would suggest creating a semi-transparent plane in front of the camera with an animated texture on it which is enabled when you want the effect.