Got a new puppy this winter and am having a very hard time keeping her in the yard. She's pretty well potty trained but the problem is that we still have to put her on a leash or she'll dart off. We live on more than an acre so we should have plenty of room in our own yard. Question being I've thought of getting a shock collar of some kind to train her to stay in the yard. Suggestions? I've heard there are units that you plug in and start to shock if they wander away a certain amount of feet....help! I should probably note that I'm not going the underground route...way to big a yard imo and I don't want to hassle with tearing up my yard like that.