Well, you would be facing a few problems with the idea, so give me a sec to play devil's advocate. But I will start by saying it's a decent idea, now here's the problem.
#1 Integration: DVD players (most anyway) are made to accept a certain thickness and mobility on DVD's. The plastic used to protect phone covers is generally plastic, not as unresistant as the original face, and hold by static, which can build up as anyone who has ever overly rubbed on on their pants can tell you. Static inside a DVD player is not a good thing.
#2 Application: You would have to have an applicator that would put the cover on the DVD in such a way to not imbalance it which can wreak havoc on the DVD, the player, or the user.
#3 Price and Popularity: The covers and applicator couldn't be more expensive than a DVD or most people will more than likely just ignore it. On top of that DVD popularity is giving way in a big sales drop to streaming. So your market share shrinks there as well.
Again, not trying to pee on your cloud, but these are things you will have to address if you decide to move forward, especially if you plan on getting an investment through people or banks.
Good luck.
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