I have used both products Zepp Tennis Swing Analyzer and Sony Smart Sensor. I found Zepp is much better than Sony Sensor considering below reasons. 1. Price : Less expensive than Sony but still little expensive ($149) 2. Durability : * Problem- Pops out but not so frequently while playing * Solution- Two types of mounts are available and much durable as one of them comes with 3M sticker and anther can be used under overgrip. 3. Battery : Last longer 4. App : * Simple and user friendly * Hitting zone is clearly specified/distributed with %age of shots hit on racquet. * With version 2.0 tips and tutorials are available shared by Milos Raonic and Professional coaches. 5. Accuracy : More accurate 6. Feel with racquet : Weight increases marginally but finger keeps touching the device so frequently and makes uncomfortable while playing.

I've previously tried a Sony sensor at a US Open demo, and enjoyed the experience, but that sensor was integrated into the handle. This Zepp sensor is a little clunkier partly because of it's square shape. Using the larger temporary holder, it helps to put it underneath a layer of over grip to hold it in place. Otherwise it feels pretty bulky in the hands and affects the swing weight of the racquet quite a bit. The smaller holder which you tape to the bottom of the buttcap is less intrusive and doesn't mess with the swing weight as much, but you have to tape it in place before you put the sensor on, otherwise there is no chance of it not flying of your racquet, as the small amount of adhesive attaching it to the buttcap will never hold it in place if you hit with any sort of power. Despite all that, it's a cool tool that gives you fun feedback and hopefully future iterations will be more sleek and more securely integrated into the racquet.

I don't think this product is useful for a tennis learner. It can only measure whether you hit the sweet spot, it cannot monitor your motion.

I purchased for a family member. Hope he liked. You know, for me the fact that you need to stick something at the bottom of the racquet handle is not very glad to me. The quality is fine and the functionality is easy to use.

Does not fit on a racquet. Limited utility. The holder for the device interferes with a normal grip. All-in-all, a complete waste of time, money, and effort.