What is a good dog for me?

So my sister is going to college in the fall and I will be an only child, which is sad because we are best friends. So I'm sort of looking for a dog to keep me company but need a low maintenance one who doesn't shed too much. The thing is I wont be home during the day so I don't want it to go stir crazy. And it would be good if it also was a watch-dog type dog. I hate small yip-yap dogs. They annoy me. Any suggestions?