re: Invisible Fence for Dogs

The house is on about 2 acres with woods surrounding. No need for a huge ugly fence, but my dog has been getting brave and taking off through the woods. The highway isnt far off and I'm scared he will make it out there. I've been using my shock collar for now when he starts to take off, but I want to be able for us both to be outside and me not worry about where he is wandering.