I did the same thing for my son. I sent him the absolute necessities, undies socks etc.
I think it was the right thing to do too. He's fulfilling his punishment. I couldn't imagine letting him go with out those basic things. It's the mom in us. We want our kids to have their underware!
I can remember when my mom kept spare undies in the glove compartment of the car. She said it was in case we had an accident. I have had other friends tell me their mom did the same thing too.
Looking back, I think that has to be the most ridiculous thing I ever heard. I mean, if we're all in an accident, I doubt the first thing we would do before being loaded into an ambulance is change our underware! I guess she imagined a car accident to be nothing worse than getting a cut on your hand. The one where you didnt' get hurt so bad that you couldn't change your underware.