My son got mad at a game and broke his Ninteno DS. I think I found the perfect punishment?

Well, I'm not a mother yet, but in my opinion you should make him pay off his DS. Grounding him won't solve anything, it will just make him angrier. You can take away allowance or make him get a summer job (i.e. mowing lawns, walking dogs). It will teach him good work ethics and the value of money, plus to respect his toys.