I found that physically removing his PS2 and GBA did wonders, as did unplugging the computer and removing the adapter (we are posted abroad with the Armed Forces).
I would not do a DD for pocket money -when asked why at the bank, I pointed out I couldn't stop pocket money if I needed to.
My lad is 12, and has to keep the loos stocked with toilet rolls; to clear the table after each meal; clear his room before the cleaner comes each week; and be pleasant most of the time. He is not allowed to moan when food shopping, and has to help put it away. For this he gets ?20.00 per month. I pay for clothes, lunch at school etc.
I am lucky in that I have said if he is not pleasant and does not help out, then he will be sent back to boarding school in the UK. This also encourages him to keep his work up at school, as he does not want to board.
I sound horrible, but it works, and for the most part he is lovely and fun to live with. He morphs into Kevin occasionally, but realises he is doing it and stops.
Embarrassing your lad in front of his friends will work, and he won't be scarred for life. It's a technique my mum used, and it worked on me. If he's 13, he's finding his feet and pushing his luck. Push back equally hard and show him who's boss - he'll get the message - he gets it in school hopefully, he should understand it at home.