Suggest to a struggling golfer that they should get lessons and you’re likely to hear one of two answers: They’re too expensive or there’s not enough time. Those are especially true for folks who don’t belong to a private club with access to great instructors and a pristine range to practice, and don’t have countless hours to grind away without feedback.

Sang Kim, the founder and CEO of 4D Motion Sports, has created a product intended to address the problems that hold golfers back from achieving their peak performance. Kim has been a serial entrepreneur and inventor for the last quarter century, working on mostly internet startups. He wanted a break after his startup was acquired by a Fortune 500 company, so he began to play a ton of golf.

“First thing that happened, I just couldn’t putt,” Kim said. “One day I three-putted 12, 13 times, and I said, ‘there’s got to be a better way.’”

Kim, a self-described “science-y guy,” realized that it was only a tiny portion of the golf ball that he needed to get into the cup to hole more putts. He put his inventor cap on, went home and grabbed his son, and they took a hacksaw to both sides of the golf ball and started experimenting. What they came up with was the PutterWheel, a product Kim later presented to a pair of “Shark Tank” judges in a competition at the ASI Convention, which he won.

“We were just mobbed,” he said. “Then we got a Dick’s [Sporting Goods] deal, we were in 750 stores. That kind of got me into the [golf] business.”

That’s when Kim realized that what he really wanted was to fix his full swing. He knew that while there were a lot of great golf instructors out there, they can’t be with you all the time, and rarely on the course. Leveraging his tech background, he wanted to create a system that can measure, analyze and train your swing anytime, anywhere.

At the time, 3D body motion capture was available, but Kim noticed it was far too expensive for the average golfer. He wanted to create something that was affordable, put it on mobile devices and make it super-fast. That’s when he came up with 4D Motion, a passion project 12 years in the making that Kim is ready to launch for the consumer.

“It’s the hardest thing I ever worked on,” he said. “If I knew it was going to take me over a decade, I’m not sure I would have ever started. But now i think we have a product that I can honestly say, it has to make people better.”

When I first tried out the 4D Motion vest and saw instant feedback on the Apple Watch, I was intrigued, surprisingly, because I’m the type that wants to know less about my swing when things are going well (surprisingly, they are right now). “That’s the goal,” Kim says. The prototype vest, which can be worn under a golf shirt, has three sensors in it, one between the shoulder blades, one on the sacrum at the bottom of your hips, and one on the chest that acts as the gateway to the phone app that picks up everything from setup, shoulder plane, pelvis speed, spine angle, and beyond. After my first swing on the range, it took three seconds for all these data points to show up in the 4D Motion app, which showed I came slightly over the top and that I extended a bit too early, which led to a pull. Those two data points were in red, signaling what I had done wrong. Setup, posture, rotation and shoulder plane were all in green, signaling those were all in good shape. Simple to understand.

On the next swing, I attempted to swing more inside to out, hoping to get rid of the over-the-top motion that can lead to dead pulls or mega slices. After impact, I felt I had fixed the issue. The data reflected that. That euphoric feeling was short-lived, however, when Kim showed me that I had a poor loss of posture score. Back to work.

You don’t even need to leave your house, or even have a club in your hands, to work on the proper positions in your swing. Put the vest on in your living room, open the phone app and you can simply get into your setup and make your turn. The sensors will pick up how your torso and hips are moving, and the model of yourself in the app will turn green and make a dinging sound when you are in proper position.

Of course, using the product at the range or inside your own home can only get you so far. What’s different about Kim’s product is that it tells you exactly what you are doing differently on the range and on the course, allowing you to identify the factors that are keeping you from swinging your best when you need it most. In a recent experiment with a low-handicapper, every swing he made on the range was in the green on the app. Then he went out to play six holes and the app revealed a number of flaws, including early extension and flat-shoulder plane.

“You get tense, you tighten up. You don’t rotate properly,” Kim said. “His biggest flaw was flat-shoulder plane. He never knew that about himself. So now he knows. With the system, you could even take a practice swing and see if you fixed it or not.”

The vest is already being used by top players as well as their instructors. Kim’s also made headway with Major League Baseball teams — the former Nationals hitting coach Kevin Long is on 4D Motion’s advisory board. It’s also been used by the U.S. Figure Skating team, where he’s developed an injury prevention system that uses machine learning to identify the jumps in a workout and detect fatigue that can lead to injury.

Soon, you’ll be able to get your hands on it, too. Kim says they are launching a Kickstarter campaign for the product because they need financial support for its production. As for pricing, Kim says they will offer multiple different packages, but final pricing will be in the $600-900 range (Editor’s note: Golf Digest is a minority partner with an even more affordable option, the Mustard Golf app that provides AI-generated feedback and instruction on your swing videos).

“My goal is to make this something that’s affordable. If you can afford a new driver, or a putter these days, you can afford this,” Kim said. “And I think you’re going to get a lot more improvement from this than a new driver.”

The product has already gone through several updates and is faster since the first time I used it. You will now be able to quickly add notes and comments, marking down what specifically went wrong or right on every swing and be able to click into that swing and see what you wrote down later.

“That’s when you can really differentiate,” said Jim Beadle, the director of business development at 4D Motion Sports and a golf instructor himself. “OK, good shot, bad shot, high draw, high cut, punch shot. You can really start to differentiate between every shot I took on that golf course.”

The whole picture, naturally, can be overwhelming. That’s why Kim is revealing only a fraction of the amount of data and technology that they have at their disposal for now. As time goes on, users will be able to unlock more and more data points that will be useful for them. Simplifying the product for the consumer was paramount.

“I wanted to help people like me,” says Kim, who is a single-digit handicap always looking to improve, just like the rest of us. “That’s what this product is all about. Maybe you can’t afford to take lessons, maybe you don’t have time to take lessons. Maybe you like your swing on the range but want to know what is going wrong with your swing on the course, where it counts.

“Golf’s one of the few sports where—imagine you met somebody and you say, ‘Oh, you play piano? How long have you been doing it?’ And they say, ‘30 years.’ And they get up there and they play ‘Chopsticks.’ That would never happen. But in golf, you meet somebody who has been playing for 30 years and he’s still a 28 handicap. Something’s wrong there, and I’m trying to help fix it.”