Once you get to consistently doing 50 pushups, you start working towards one handed pushups
The one problem being, the translation from high-rep push-ups to a one-handed push-up can be a BIG leap for most people, and that's where a lot of frustration may set in. The lighter you are, the easier it will be, but even though I can knock out about 40 push-ups in a set, there's no way in hell I can do it 1-handed without a TON of assistance from the other arm. Then again, I weigh 230, so someone weighing 170 lbs. or less may have much better luck.
one handed pullups
Don't want to rain on anyone's parade, but the lineup of people who can do a even a single 1-arm pull-up is very, very short unless you're a gymnast with exceptional upper body strength from years of training or have an incredible strength to bodyweight ratio in place from the start. If you want to know how hard it is, try a 2-handed pull-up with your bodyweight strapped on to you (or, someone your size hanging from your back), then think of it being the same, BUT, just with one arm
. My dream has always been to do one, I move about 2" before it's over with (even being able to 1-arm dumbbell row just under bodyweight for a few reps doesn't carry over on it for me). I've seen training logs of people who are champs at weighted pull-ups who spend years working to try single-arm style and never make it happen. Just wanted to note that the 1-arm chin or pull-up is a VERY lofty goal that most won't achieve, but definitely something to aim for.
handstand pushups (one handed handstand pushups!)
Again, problem being the issue of progression is the challenge. To do handstand push-ups from the get-go, you have to already have some excellent strength in the shoulders and triceps to where you can at least come close to doing a barbell overhead press with bodyweight. You CAN cheat it a bit by being out further from the wall to increase incline a bit and incorporate more chest work (making it easier), but getting to where most people can do even a few handstand push-ups is the tough spot. Unless, of course, you have a spotter to help you de-load some of your bodyweight until you develop the strength to do it unassisted.
one legged squats
See issue with push-ups again, same case in this one
It's kind of fascinating because he claims that in prison it was all he had access to.
No doubt about it, some people in prison maintain great physiques via bodyweight stuff if they don't have a yard for weight training. BUT, many of them were anything but small guys when they got there, so always take claims with a grain of salt. After all, Combat Conditioning DOES cost money and needs a gimmick to stand out!
Don't get me wrong, I'm not trying to knock bodyweight stuff hard here. It's convenient, can be done almost anywhere, and can give great results dependant on goals. The two caveats I'm trying to point out are that sometimes, it's just not feasible to make the jump from one thing to the next (such as high-rep push-ups to a single-arm one) and that there will be limitations to what you can get out of it for mass gains vs. training with barbells and dumbbells.
I wish nothing but the best of success with the program - I'd love to hear that it works out well for you, so keep us posted how it goes!