Are there movements on this device that work the legs and hip complex? For now, the kettle bells you have would be a great start. Simple movements such as goblet squats and overhead presses are a good start.
I would HIGHLY, highly recommend reading Starting Strength by Mark Rippitoe.
I was fortunate enough to work with a man named Dr Jordan Fiegenbaum. He owns Barbell Medicine, and I would also recommend his site, blog, and information. His claim to fame is the strongest medical Dr. in the country. ( I guess for his power lifting weight class) He knows his stuff. He worked for Starting Strength ( they produce seminars and certifications based on Mark's book) and his reasoning through each subject is straightforward, logical and effective. The best article I have ever read on proper bar grip was Jordan's 5 or so page masterpiece called Gripping Matters.
First, I'll say that finding something that gets you excited about working out is worth it's weight in gold. It does not matter if more efficacy could be gained from other, less exciting (to you) methods. So if this contraption will get you working out, and other wise you would not, then go for it. There are better ways to get strong and in better shape though, in my opinion.
Practicing movement on a machine makes us better at movement on the machine.... the benefit does not transfer to your life 100%. Read up on closed chain vs open chain movements. Most folks use the workout as a means to an end. If that is the case, then something with more efficiency and carry over to real life would be a better option unless time in the gym (or the fun of working out) is the goal.
Doctors of internal medicine, which most people refer to when speaking of a doctor, are obviously intelligent people. Their specialty is internal medicine, however. By profession, doctors of internal medicine are generally not educated in the movement sciences, nutrition, and physiology as it relates to human performance and exercise. The most common recommendation from doctors from what I have seen is to walk. Next, they recommend to use machines. It is not because walking or a machine is the most effective exercise, it is because it is an easier recommendation to give. First, one can express it in a single sentence. Second, free weight suggestions by someone unqualified to give advice on free weights will absolutely result in an injury given a large enough sample size, opening up a doctor for possible liability claims.
From my years as a trainer, and then trainer of trainers, one of the biggest mistakes folks make when coming up with a plan for better fitness is not knowing what their goal is. Getting into better shape is not a concise enough goal to be effective, for instance. Another mistake is to not train for the goal. Much of the time, not only is nutrition usually not supportive of the goal, but usually not supportive of the additional expenditure caused by the exercise in the first place. I see guys who have limited time and energy waste some of their valuable resources on movements that do not get them towards their goals. Their prioritization is way wrong.
Take an overweight guy in his 40's for example. If he had 2-4 hours a week to workout, spending any time every week on low yield movements that isolate small muscle groups such as forearm curls, shrugs, calf raises, sit ups, "ab" machines, bodyweight movement etc. will reduce progress towards a goal to a near standstill after the initial adaption. Conversely, progressively loaded, multi-joint, compound movements based on the pattern of movement all humans share would be ideal because they can be loaded almost indefinitely. Humans have 7 movements that we generally perform, and loading these or similar movements is very efficient. Squat, Lunge, Bend, Twist, Push, Pull and gait (walk). I do not recommend loaded walking, pushing/pulling a weighted sled short distances is fantastic.
