Can This Gadget Turn You Into Rafael Nadal?

I've made peace with the notion that I'll never run point for the Celts in the NBA finals, shoot a 63 on Sunday at Augusta, or bagel Rafa in straight sets on the Roland Garros clay. I'll forever be a sad-to-middling weekend athlete. And yet I like to imagine that I still have potential for improvement.

I'm not alone. There are millions of plodding, athletically challenged, wannabe jocks out there scouring YouTube clips for coaching tips, enrolling in lessons from local pros, and buying bizarre and, frankly, embarrassing instructional aids.

The latest trend in sporty self-improvement: sensors that analyze your physical form and give you instant feedback. A wave of new consumer devices-packed with teensy accelerometers, gyroscopes, and Bluetooth transmitters-promises to track the speed of your golf swing, the shape of your tennis stroke, and the backspin on your jump shot.

I tested out a few of these products to see if they'd boost my skills. Could technology help me morph into a beast in my weekly hoops game? Give me the skills to crush my regular tennis partner? Shave precious strokes off my disappointing golf scores?

One must acknowledge a fundamental weakness with these sports sensors: Simply knowing, say, how fast you swing your 7-iron does not at all translate into hitting a golf ball straight and true. Improving in an athletic endeavor requires a collection of tiny, subtle adjustments. Tweaks to your stance, rhythm, balance, alignment, fluidity. Only a trained eye will be able to watch the whole motion and identify its weak link.

Still, while they won't immediately launch you onto the front of a Wheaties box, some of these sensor products do offer useful functions. Herewith, my rankings on the country club ladder, ordered from worst to first:

There's something pleasingly sci-fi about a tennis racket with a mini-USB port hidden in its handle. Pop open the Babolat's butt cap and it's hard not to feel you're peering into the future of sports. The promise is obvious: Play a set or two, plug the racket into your laptop, and download an instant, detailed analysis of your performance. I couldn't wait to take this thing out for a spin at Midtown Tennis.

Sadly, the reality was far less fun. Despite repeated efforts, I couldn't get this thing to work. Scads of online reviews confirmed my suspicions: The Babolat is buggy. Though my computer recognized the racket, it failed to locate any data from my on-court sessions. I called up Babolat, which acknowledged the bug, promised me it's working on a long-term fix, and gave me instructions for a short-term workaround. I followed those instructions closely, yet the racket still failed.

Even if the Babolat had performed smoothly, I see a core problem with its model. What if you prefer a racket with a larger or smaller head size? What if you'd like to be able to swap in, mid-set, a backup racket with a different string tension? Or what if, heaven forbid, you break a string? Because the sensor is buried within the handle, and the handle is nontransferable, you're forced to play with this particular $400 racket if you wish to record your data. Seems like a fatal flaw. And one that could be easily obviated-as demonstrated by our next competitor: