T.T.
The worst punishment my mom ever gave my sister was when she was lying about going to school...my mother in all her muu muu glory, walked my sister up the front steps to her highschool and WALKED her to her first class just to make sure she got there. Humiliating...yes. Effective...ABSOLUTELY.
The point is there IS a way to get through to him, but I think you're looking at it from the wrong perspective. Instead of ways to punish, I'd be trying to find a way to have him do OK. He won't brush, brush for him or stand and watch him do it. If he's not doing homework, stop everything and sit next to him and do that too. Keep an open line of communication with his teachers. Email or call them every day. I did with my oldest son. I won't GIVE HIM A CHANCE to mess up.
I don't think the DS or the TV is a good incentive to be "good". When my son started lying, every time I caught him in one, something disappeared from his room. Pretty soon...he lost everything but a bookshelf and a sleeping bag...and the door was off it's hinges and sitting in my garage. After a while of loosing EVERYTHING...he realized that trust is an EARNED thing. And I didn't scream and yell either. I simply told him what was going on...and took what ever it was away.
Being a parent is a proactive, 24/7 work in progress. It's not for the weak of mind or spirit. And being a parent means you have to be more than a friend to them.
Odds are your young person needs some attention he's not getting (by no fault of your own)...make it positive not negative.
For the record, my son was gifted too...and very self correcting...that was a HUGE issue with me when he was growing up because I'd ask him...if it were you...and this happened...what would YOU do?? 9 times out of 10 he took the high road and said...get mad/get punished/get grounded/etc.
I trust kids as far as I can pick um up and carry um. It is thier JOB to push. It's our job to hold true.
Good luck to you. I'm sending good thoughts your way!