I second the money idea... I know it is not personal but he can exchange them money and get something they need when they are in Korea.
While I was in Bulgaria for a few years I appreciated the cash gifts a lot more then anything else because I could exchange the cash and get something in Bulgaria that I wanted or needed.
If you want get the cash in Euro and they can use it in Germany or in Won (which is the Korean currency). That way it will show that you are thinking of where they will spend it and save them time in exchanging it. Plus when you exchange money most places take a percentage fee so they end up getting less of the gift money. Just an idea!
P.S. I would not go with a gift card... I have always had a hard time redeeming them overseas. Also even if you use them online sometimes the order would never go through yet the gift card is drained of its cash, so you could never use it.