I don't let DS out in the back yard on his own just yet, unless I need to dash to the loo.
I can't see too much of the back yard at all from the house so I usually take the laptop outside and sit and watch him while I'm on BB!
We're about to build a house which will have a fenced off area to the side of the house which will be DS' play area and he can come and go as he pleases!