A couple of friends of mine are doing the same this year through EPIK, a South Korean government run program. I was looking at doing it but it seems to realistically do it, and make some cash at the same time, you need a bit behind you to start with, which I didn't.
But apparently they are one of the better ones to go through. There are a fair few stories online of people essentially being scammed in S. Korea through these English teaching programs, so I think I'd prefer to go through one run by their government than a private company.