Not to sound holier then anyone, but I don't see any reason for containing a child to a playpen or small area while you go to the bathroom, or another room. To me small children are just that: little people who need to learn and understand why things are done and how things work. If you're going to the bathroom, explain the potty concept while you're in there. Show him how the lid works, tell him about the tissue, show him how to wash his hands when he's done. If you're in another room ironing or folding laundry show him the ironing board and teach him to collect the socks for you into a pile.
I guess this takes more time and makes chores longer, but really aside from emergencies, I just never saw a good reason not to include a child in day-to-day activities.
However, if you need to contain him for some sort of hazardous situation (dropped a glass and gotta clean it up) use a gate or try to playpen tent...I can't attest to it's value since I never had one, but it seems it would work for a climber.
Anyways, you're obviously a caring and nurturing person or you woulnd't be making the sacrafice you are, and I commend you for it!