I've made some modifications since these pictures.
Including adding more screws, tightening everything up in general and getting a larger (and not bent) bar.
I'm still planning on adding a little bit more.
A rope, a thicker bar at the top, another bar at the top, a counter wait for the climbing bar, etc.
Here's a video of Noah.
And one of me. Sorry about the camera, my cameraman must have been on drugs.
Still not sure how long it will all last, it seems to hold up pretty well to Noah and he's about 240 but we'll see. I used all pressure treated wood and fancy, coated decking screws. I also painted the exposed ends of the 4x4s with redguard (And one of these days I'll coat the downward facing screw-holes in roofing caulk). The basic instruction video I followed can be found here.
The stuff they say about wanting a crash pad and something to stop the bar from falling and 'slammin' into your head is pretty true. This thing terrifies me. Anywho, happy climbin'!