...and sometimes overpriced!
What these pushup bars allow you to do is simulate the optimal lifting technique if you were doing a bench press using dumbbells (DBs): at the bottom of the bench press when the DBs are next to your chest, your palms are facing each other in a "hammer curl" type of position and as you push the DBs upward and away from your chest, you rotate the DBs inward (counter clockwise on the right and clockwise on the left) so that at the top of the movement your palms are no longer facing each other but your thumb knuckles are facing each other instead, and you might gently clink the dumbbells together for good measure. By adding a twisting motion to the pushing motion, you will feel a deeper flexion over more of the chest muscles including the insides of your pecs, rather than just the outside of your pecs next to your deltoids. This is the other reason that DB bench presses are essential, though obviously you can lift more poundage using a barbell (the main reason is that you will strengthen both your left and right sides of the body more evenly).
Just as you will find that you won't be able to use quite as much poundage doing a twisting DB bench press rather than a non-twisting linear DB press, so with these twisting pushup bars you will find yourself being able to do fewer repetitions than with normal fixed push-up bars. That is really the main advantage of these "Perfect Pushup" devices: you don't need to crank out as many reps to get to the same level of exhaustion. I normally can do around 30-40 reps per set with normal pushup bars, 50 reps per set with no bars just the ground, and only about 20-25 reps per set with these "perfect pushup" bars. This means you get a faster, more efficient workout. And if you are prone to rotator cuff issues, also a safer workout as long as you don't space these bars too far apart. They work best at shoulder width and especially, closer in---which makes perfect sense, since if you were doing a twisting DB bench press you would hold the DBs much closer together than if you were doing a barbell bench press.
Now the big caveat here is cost to benefit ratio. Normal pushup bars can go for as little as eight bucks, so you need to consider if it's really worth it to pay five times more for these "perfect pushup" ones. (I did find them at Wallyworld for twenty bucks though.) The claims of these things giving you spectacularly better results in mass and definition are, of course, just a bunch of sales hype.
Either way, pushup bars of either kind are a HUGE improvement over just plain 'ole pushups off the ground...less carpal tunnel syndrome risk and much fuller range of motion.
PS. The best way to get a great chest workout at home would be to pre-exhaust your pecs with say 3 sets of 6 to 8 reps of DB pectoral flies with moderate weight, and THEN do the pushups! Otherwise what often happens is that the delts and triceps get tired out before the pecs (a much larger muscle) are completely exhausted.
PPS. There is an alternative way to do pushups WITHOUT handles of any kind, and WITHOUT any carpal tunnel syndrome risk: do them on your fists, with a folded up washcloth or other padding under your knuckles if needed. I got this idea from scoobysworkshop dot com, which btw is a TRULY EXCELLENT resource for home workouts without a whole lot of equipment...tons of instructional videos there which are also available on YouTube and it's 100% free.